The Winter Park or Winter Park/Copper Mountain (Super Pass) or Winter Park/Copper Mountain/Steamboat (Super Pass Plus) options have been mentioned several times before in this thread, and I can definitely endorse any of those options for your situation. I started with Breckenridge, Vail and the other I-70-west-of-Eisenhower Tunnel areas as a new skier badly bitten by the bug 25 years ago when I lived in Kansas City. I know all of those areas quite well. In the intervening years, I have gotten to know Utah's offerings extremely well, and also have put in probably 15 days at Taos to boot. Since moving to CA, Mammoth is ostensibly my "home" mountain, but I have found, in the last 3 years, that I am quite fond of Winter Park. I started meeting my brother and his family there 3 years ago as a family friendly place that is one of the most affordable ski areas I have ever been to. If you do spend the night, you can find great condo deals through VRBO. The single area WP/Mary Jane season ticket, at $369, is hard to beat (Mammoth this year is $770), and your son's ticket is $209. (I hate to mention it, but if you had bought your ticket by May 22, your son's would have been free) Between the two mountains, there is something for everyone from never-ever beginners to the most challenging of double black bump runs. I even have found the Eagle Wind area and the Vasquez Cirque to be pretty much as satisfying a powder experience as Little Cottonwood Canyon, the powder lasting way later in the day. (I didn't say as good as LCC, so no flames please, you other bears out there ) So,there's plenty there for your family to develop in to. I don't know the drive all that well, since we usually take the shuttle from DIA, but it seems shorter and less of a hassle than the drive to Summit County/Vail. There is one pass to deal with, but I don't think it is any worse than getting up to and down from the Eisenhower Tunnel.
Anyway, I just wanted to put in my two cents as far as what I might do if I were in your shoes, knowing what I now do.