Not sure if this is a thing anymore, been a few years since I’ve skied out there, but they used to sell something called a Summit County Pass. It essentially allowed you to ski the 4 big resorts that are basically a golf shot from each other…Breck, Keystone, A Basin, and Copper. It allows you a change of scenery if you want.
If your son is a snowboarder, what type of riding does he do? Breck by far is going to have the best terrain park, followed by copper in my opinion. Breck also has the most skiable acreage, and access to 4 different peaks if he really wants to get off the beaten path. From what I remember, Keystone was the only one that had night skiing, but like others have stated, you may not get sick from the altitude, but skiing/boarding out there is a complete different beast. I never got sick, but you’re quick to realize your quads screaming at you from lack of oxygen. Afton Alps or Mount Kato don’t prepare you for that. Also add on the fact that some runs in Breck are literally miles long vs. the 100 yards we’re used to in the Midwest. You might have a tuckered out son by 3 in the afternoon.
Definitely bring groceries…a burger on the mountain will cost you $12, with nothing else. In town won’t be much better. Pack simple food in a camelback with some water for the mountain. Easy to bonk quickly out there.
The number of snowmobile rentals out there will be endless. Google search yielded 3 within a few minutes drive.
Have fun!