I wish I had seen this before now-- hope you're still checking in.
We live in Colorado with our two boys (ages 3 and 6) and are big fans of childcare/ski school at both Snowmass (gorgeous facility built only a few years ago) and Steamboat. We have also used Vail a lot, and while they are perfectly fine for kids (and ours have had a good time, particularly in childcare), they just aren't as well set up/new and shiny. What I will say in Vail's favor, though, is that they offer Micro Mice for kids over 20 months, and that allows them to go out and play a bit on skis 1-2x per childcare day. That's a pretty cool feature for only a small add-on in price.
What's to like about Steamboat:
Ski school is very friendly & upbeat, and they have a great, separate school section for kids kindergarten and younger. That means they have their own lunch area and play area (when they get too tired and need an inside break), so you don't have to worry about them wandering around the cafeterias on the mountain. I found them to be very good about getting kids up to nice learning areas on the mountain as soon as they are ready (instead of just inside the fences at the bottom) and all of the teachers we had contact with were SUPER upbeat and enthusiastic, which is nice for the little ones. They seem to attract a crowd that actually likes teaching children, instead of people who feel like it's punishment. Also, for your younger one, they have a program for the little guys to go our for 1-2 hours with a private instructor, and it's awesome. I am blanking on what it's called right now, but it's worth looking into. A little pricey, but they set the childcare kids up with all the equipment and just teach them to have fun playing on skis. Really fun if you want them to try a tiny bite of instruction when they are small. Only downside at Steamboat is carting all the piles of kid stuff to the hill, as it's up and down stairs, etc. (older village design), and all the way through the ski village. We rented from a group that offered storage in the village as part of the rental (plus, we were within easy walking distance) and that made it much more pleasant. Also, the other *down* note is that much of the skiing isn't terribly steep, and it might get dull for the grownups after a few days if there isn't new snow. If there
is new snow, however, the more difficult tree skiing is
LOADS of fun. Laps of smiles all day long.
What's to like at Snowmass
The ski school and childcare are gorgeous and shiny and new(ish). They have a good caregiver/teacher-to-child ratio. They let you leave the whole ski bag (with layer changes, etc.) in a cubby for your ski school child, so he/she can actually have clothing changes, instead of just dropoff in one outfit that might be all wrong. The facility has really fun stuff for when they come inside for breaks-- foosball tables and the like, so they're not just sitting there when they come inside. It's built in the new village below the old Snowmass Mall, so they make use of the small cabriolet-style gondola up to the Mall once kids progress past the magic carpet (a lift ride without the trouble of loading a class full of wee people onto an actual lift) and there is also easy access to the other gondola servicing the base, which goes up to another learning area. Makes getting small children up onto the mountain a piece of cake. The childcare is very well staffed and clean and cheerful-- no daycare dungeon here. The major downside is the parking/traffic situation for drop-off if you don't take the bus, although I think that's gotten a little better with the new underground garage. Also, if you want to ski Highlands, you have to contend with drop-off at Snowmass, driving over to Highlands, and making sure you get back in time. However. . . on days when the kids need the day off & you still want adventures, there is an excellent babysitting service in town--
https://www.amomsdayoff.com/ -- and you can have someone come and play with the kids for a few hours while you ski. We have had excellent luck with this sitter service, and we are not big sitter users. Oh, and as you know, terrain around Aspen/Snowmass is awesome.
Here are some links to trip reports from recent family trips/weekends in Colorado, if you want a better sense of what some of the areas are like with small children:
Winter Park, March 2010
https://www.theskidiva.com/forums/showthread.php?t=9675
Steamboat, March 2010
https://www.theskidiva.com/forums/showthread.php?t=9468
Couple days in Vail, February 2010
https://www.theskidiva.com/forums/showthread.php?t=9332
Aspen/Snowmass & Vail, March 2008
https://www.theskidiva.com/forums/showthread.php?t=3550&highlight=snowmass