The vail resorts will be packed at this time. I'm not telling you not to go to them, but understand that long lift lines are going to happen during that part of the year.
I would say visit Vail or wherever you want to go. Then spend some days at Loveland, Beaver Creek, or Copper Mtn. These places are going to be less crowded during Christmas because they are a little out of the way and people tend to spend all their time at Vail, Beck, and Keystone. I'm sure you will have a great time wherever you go but if you don't like crowds, go to the ones I suggested.