Angie Harrington Celebrates Son Hart's 5th Birthday with a Shape-Themed Party: 'Grown So Much' (Exclusive)

The mom celebrated her youngest after a transformative year for their whole family

Angie Harrington is one proud mom.

The Real Housewives of Salt Lake City alum and mom, 42, celebrated son Hart's 5th birthday with a special celebration for the birthday boy, who was diagnosed with autism last year.

Speaking about the special event with PEOPLE, the mom of three says it was important to her and her husband Chris Harrington to have a "very low-key celebration that was about whatever Hart felt like doing that day."

"We felt like five was such a milestone that we wanted to do something really special. We realized a lot of our friends will throw family events or movie nights or things that Hart doesn't really do great participating in because of his challenges. Sometimes, he gets overwhelmed when he's familiar with the place, and he's extremely hyperactive," Angie tells PEOPLE.

"Because we typically have to leave him home with a nanny when we do those kinds of events in big groups, a lot of our friends know Hart, but they don't know him as well as we would like. They don't realize how special he is, so we wanted a party where we invited everybody over and did it all on Hart's terms. That way, everyone could gather and see what beautiful energy he brings into a space."

To make the party Hart-approved, they opted to have the celebration "in our backyard, a space where it's very familiar."

Angie worked with a team that's familiar with putting together special events for children with autism, with the reality TV alum crediting Events by Janelle for "setting up in a way that really helped Hart acclimate."

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Related: Angie Harrington Reveals She's Leaving 'Real Housewives of Salt Lake City' to Care for Son with Autism (Exclusive)

"My party planner, Events by Janelle, was great about coming early and setting up slowly. I'd take Hart outside as she was setting up so he could really acclimate to what was happening and the party. And I think that really helped because he didn't seem to be totally overstimulated," Angie explains.

"Autistic characteristics show up very differently for each person. Hart's main characteristics would be lack of eye contact, speech delay and hyperactivity — the kid is a party animal. We felt comfortable having this event because, fortunately, overstimulation doesn't tend to be one of his sensitivities."

The theme, shapes, reflects one of Hart's biggest interests at the moment.

"Hart and other kids with autism tend to have special interests and one of his is shapes. He does have a speech delay, but the kid can probably name 200 shapes — half of them which I've never heard of," she laughs.

"We had pizza triangles and fruit skewers in the shape of stars. It was really fun, and I realized how great birthday parties can be for kids with autism if you really cater to their interests. Hart stayed very interested and engaged and less stressed out than I thought he might be, so that was a win."

Leading up to the event, Angie "tried to prepare him and tell him, 'We're going to have a birthday party and there's going to be a cake.'"

"He listened to every word I said and then looked at the door like, 'Let's go,' because he thought we were going to a birthday party that day. So then I realized I couldn't talk about it anymore because he wasn't grasping that it's coming up and it was bumming him out that it wasn't that day. The day of, though, we got off to a good start. We did his morning Starbucks run, which is very important to him. He loves his egg bites. So we did that and came back again."

She continues, "My event planner really let him slowly acclimate to what was going on. She let him come out and touch the balloons and the streamers as he looked around at all this action. You could tell he got excited. He started jumping up and down. He turned to me, and he went, 'Kiss, kiss!' He's like, 'I've got to get this energy out. I need a kiss, mom!' So that was really sweet."

The parents were thrilled to feel like the event was a resounding success, with Angie's favorite moment being "seeing all the people we love most gather around and sing Happy Birthday."

"It was my family, Chris' family, all our friends and some of Hart's friends. Being able to realize how much love there is in our lives and how many wonderful people we have, and our little boy has, was such a beautiful sight."

As for the birthday boy, he was all about the cake.

"He could not keep his eyes off the cake," Angie laughs. "By the time we cut the cake, there were little fingerprints in it. The cake had rainbows and shapes. It's funny because there were so many things going on in shapes and theatrics and he was so zeroed in on the cake. So it was pretty cute."

Since receiving his diagnosis, "Hart has grown so much," as has the family as they've learned to understand his needs.

"With the therapy we have him in, he's doing so well. He's still high maintenance in that he constantly wants to be doing something, but we've learned so many incredible coping skills that have made life a lot easier and smoother."

Of course, there are challenging days as well. "It's forced all of us just to really become better people, because of the level of patience it requires to raise a child with autism. I would have never thought I had it in me. But you have to rise up and make it work, and the whole family has come together," Angie shares.

"We have a daughter-in-law who is a speech therapist and works with children with autism. So whenever the family gets together, like at the party, she's so wonderful with Hart. She's really his favorite person in the family, besides his parents. We really feel like we have a group of children that are just so sweet with him and so good with him and it's made us all better people. And it's made us more compassionate towards families with children with disabilities."

Angie says it's been eye-opening to confront the anxieties these families face.

"There was a while there where I felt so overwhelmed. There were days where I felt like, 'I don't know if I can do this. This could be forever. How am I going to handle this?' I didn't realize the fears that parents who have kids with disabilities deal with," Angie says.

"They worry about what will happen to their kids when they're gone if they need forever care. There are a lot of anxieties that arise, but as time has gone on we've focused on doing our best for Hart. We joined the board of directors for a program called Wolverines Elevated at Utah Valley University. It's basically post-secondary education for folks with cognitive disabilities. What I didn't realize is there's no clear path for education for these kids with disabilities. I had no idea there really isn't an opportunity to attend college."

Research surrounding the program and others like it say that "a large percentage of these students end up having much more fulfilling lives and better jobs, and they're more likely to become independent. We feel really proud about educating our community and hopefully the world on education for these folks with cognitive disabilities because a lot of these kids will leave their high school programs and significantly decline. This helps kids like Hart evolve."

Reaching out to the community and making connections has been important to Angie, who has heard from many people since disclosing Hart's diagnosis.

"It's interesting because it's almost like an unspoken language. You see another parent who has a child with autism or another disability and it's like, 'I get you,' " she says.

"I'm connected to a lot of other parents of children with autism on social media. We have our DMs to remind each other to hang in there and show our support because there are always good days and bad days. I have one friend whose son with autism, right now, is into swallowing things. She told me he's constantly choking on things, which at 8 years old isn't what you necessarily expect to be dealing with. So I lend my support as much as I can and I know they're there for me, cheering me on when I need it."

Angie is soaking up all the moments of joy she gets to spend with her little guy, who continues to show an appreciation for music and dance.

"He loves to connect over music and dance. In the car, he loves Fleetwood Mac. I'm not sure where this came from, though I am grateful he's got good taste in music. I love classic rock myself. But whenever we get in the car, he asks us to play 'Everywhere.' So now we listen to 'Everywhere' in the car all day, and he's so cute in the back of the car, singing it."

At the end of the day, Hart loves taking his place "lying between Mom and Dad."

"I think that's his safest spot in the house. Once he's got all his wiffles out, we gather in bed and he goes under the cover and giggles. I think it's really his happiest time of day."

Angie is enjoying the "peace" in her life since leaving RHOSLC and knows the move was right for her.

"My nervous system is calm. I'm not constantly anxious about who I'm arguing with, or who's coming from me, or what conflict I'm dealing with. That's been nice because I've been able to really give my children so much more of me, from a less stressed-out place, which has been really beneficial for my family."

TV might not be entirely out of her system, however, with Angie entertaining a return around her greatest interest — the paranormal.

"I'm going to start going to a metaphysical school. I am a big paranormal nerd and I have done hours and hours and years and years of research on the paranormal and now I am going to become an expert rather than just an enthusiast," the ufologist says.

"I've been talking to some production companies and different potential opportunities on possibly getting back in the TV space in the field of paranormal and ufology. It's quite the pivot but isn't the world ready for it? I think we're all looking for answers and there's not a lot of females in this space, so I'm excited for the future and what it brings with that."

Though Angie's no longer watching the Bravo series, she says the castmates she continues to stay in touch with "will update me on what's happening."

"I know a few of the new cast members, although I can't say more there," she teases. "It'll be interesting to see how it goes for them. Sometimes the girls will lean on me, so I'm able to give a little advice before the process starts, from afar. I also keep my distance in some senses because I remind them there's a reason why I left the show. I'll always love them, I'll always support them, but I can't get too involved anymore."

The women she does speak to are supportive of her decision to step away and focus on family. In fact, a few were due to come to Hart's birthday party until they learned it would conflict with their cast trip.

"I think it would have been a little bit of a reunion, which would have been fun. They've been so supportive of my journey. I'm sure we'll have a nice little reunion around the corner, soon."

Angie and Chris also make sure to take a little time for themselves.

"My husband and I are going to London soon. It'll be nice, and it's the first time we've been to Europe in a year or so, so we'll be traveling. We'll be leaving Hart for five days. We can't leave him for more than a week. It's too challenging, and we just try not to do that."

The couple is also all about making memories with the rest of their blended family. "My boys are heavily involved in sports, so there's a lot of baseball and football going on," she shares.

"And for me, I'll continue my path in the paranormal field and see where that leads me. I'm really enjoying my space as a really present, available, calm mother. I'm really trying to weed out anything that will take my energy away from my children right now. And so that's honestly brought me a lot of joy and I've realized how healthy it is for my relationship with Hart."

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