Any ski trip is a gamble if you aren't a risk taker, but it's a pretty good bet. Last year Colorado had a very weak start and didn't come in to it's own until... February or so. It happens, but you have hedged your bets well, booking in February and I've never known Whistler not to open at all or shut so historically you're odds are very very good for a great ski week. The village is lively and fun with lots of activities on top of skiing, with almost 5200 vertical feet and 8100 acres of ski terrain it can be half closed and still have more terrain than most resorts in North America. The top two thirds of Whistler is still equal to the largest resorts with Great Terrain. Worst case scenario, if the snow was not everything you wanted it to be you are in a good position to do an over night trip to one of the not so far awesome BC resorts, like 6 hour trip to Revelstoke, or go heli ski a day, I've never had a bad trip to BC, scenery is incredible, and there's lots of things to see and do. A day in Vancouver is extremely popular also as people beat themselves up on the terrain and take a day off midweek. I'm sure you'll have a great trip.