Thank you all so much for the wonderful suggestions. We had a great week in Colorado and definitely fell in love with this state. A quick recap and hope others would find it helpful in the future:
Snowmass
1. Snowmass is a beautiful mountain and a very well managed resort. Many staff around whenever wherever we had questions. Almost all chair lifts have lift/trail maps with all the planning information readily available. Despite on a holiday weekend, the lift lines were nowhere near what we experienced in Tahoe resorts on normal weekends. With the free and frequent shuttles, we didn't drive and didn't suffer from the traffic jams nor parking lot nightmares which are very common when we go to Tahoe resorts on weekends. The only crowded place reminded me of Tahoe resorts was the Elk Camp Restaurant during the lunch break.
2. Renting skis from Four Mountains may not be the cheapest(and their skis are pretty beaten up), but its convenient locations and overnight slope side storage saved our time and energy which is very valuable for me as the only adult traveling with a kid.
3. There are indeed several
mountain tours open for kids! Only the First Tracks tour requires participants to be 11 and older. My daughter and I did the Ambassador Tour on day one. It was a great introduction of the mountain on a snowy day with poor visibility. On day two, we did the ACES Ski Tour with a naturalist who taught us several interesting facts(animal tracks in winter, the mammoth discovery site, trees and fires and animals, etc) about Snowmass beyond skiing.
4. We didn't have the time to explore Buttermilk nor Glenwood Springs this time, but Snowmass' coaster and tubing rides, the terrain park, several unmarked/hidden trails through trees as well as the s'more after a day of skiing were exciting experiences for my daughter. And believe it or not, riding gondolas and shuttles were fun activities for an 8 yo as well. In addition, Aspen, where we stayed, has a long time tradition called
Wintersköl from Jan 13th - 15th. On the night of our arrival, we were pleasantly surprised by a torchlight decent, bonfire and fireworks a couple of blocks from our lodge.
5. The Aspen APP is very easy to use and the rewards came along makes eating at the resorts much more affordable. Have lunch at UP 4 Pizza was a good motivator.
6. I was greatly impressed by the number of uphillers we saw at Snowmass.
A-Basin
A-Basin is surely a unique place with the base sitting at the elevation of 10,780ft. It also has a restaurant at 12,000+ ft high (claimed to be the highest restaurant in north America). Maybe because we were there on our last day of the trip, we didn't feel much of the altitude effects.
As mentioned on A-Basin's website, its terrain has varied conditions - some part were hard/icy, some part were thin with exposed roots/rocks, but most runs are well packed with great snow condition(we mostly skied blue runs).
We especially love that several runs at A-Basin have a natural dip that requires us to plan ahead for speed build up when going down in order to get up on the hill ahead effortlessly. The tree runs in Zuma Bowl area were my daughter's favorite.
A-Basin has a Ski with a Ranger program, but it only goes over green runs and my daughter wasn't interested so we skipped it.
Last but not least
My daughter is not a hard-core skier...yet. There were moments when she can't stop complaining too cold or too hot, either her hair bothers her or her goggles bothers her. One the first day at Snowmass, she refused to ski any more after the lunch break. But the other 2 days we skied this trip, we logged at 14,000+ vt. ft. and she was having fun. We are both looking forward to the next ski trip.
BTW, due to a winter storm in the forecast on our planed day one at A-Basin, we went to Keystone Nordic Center for XC skiing instead. I think it was a better option during a stormy day (others told us there was a white-out condition on the mountain and very windy that day). The Keystone resort also seems to be a very family friendly destination. We were told that there are forts on the top of the mountain but we ran out of time despite free kids lift tickets offered by our hotel.