Hi DC Neighbor -
I can't give you details about Vail, but if your son is anything like my daughter (now 10), he will likely enjoy things like arcade game rooms (arghhh!), the swimming pools, snowmobile and sleigh rides, etc. My daughter even enjoys seemingly mundane things like going to the local food and hardware stores because it gives her a chance to look them over and compare them to home.
One highly desirable factor to look for in all activities is the potential presence of other kids, especially ones that he has seen/met previously at the resort.
Once he realizes that there will be other kids there, this desire to socialize makes children's group lessons surprisingly palatable to them. Once, the SS placed her in a group with all adults because there were no kids groups at her level. She apparently did better than all the adults, but in spite of that, she absolutely *hated* the lesson because of the lack of other kids.
Also, if he hasn't had a lot of experience being away from home on long vacations, expect "I miss Mommy/home/pets" comments to start much earlier than you might prefer. IMHO, its better to cut the trip a bit short and have the kid wanting to come back for more rather than being homesick for the last few days.
Just my $0.02,
Tom / PM