THIS.
I skied Park City/Deer Valley with my daughter a couple of years ago. It had been probably 25 years since I'd skied the west last. While I'd never had any issues with altitude in the past, having skied the peaks of CA/NV/CO numerous times in my 20s, my 53-year-old self was not prepared whatsoever. Park City's base is at nearly 7,000 feet. This means you're not only skiing at altitude, you're sleeping at altitude. That's where the rub came for me. I experienced "periodic breathing" which completely freaked me out. I had no idea what was happening to me when, multiple times over the course of the night I woke up gasping for air. Thought I was having a coronary or something. It nearly ruined my trip. Imagine having such a lousy night's sleep and then getting up and thinking "I've gotta ski Park City now". And then, it happens the next night, and the next night, until you leave. I tried chugging oxygen from one of those aerosol cans, but it didn't help. Perhaps if I'd acclimatized a day or two in SLC at 4,000 feet things would have gone better. Be forewarned!
I would also say to the OP that Park City would check all the boxes for both downhillers and non-downhillers. Nordic skiing is big there. Additionally, they have a very efficient and FREE public transit system which eliminates the need for a rental car while you are in town. And, while you are there, make sure you ski Deer Valley (assuming there are no boarders in your fam, DV prohibits them). It's a real throwback and a treat.