Whistler is great, but very expensive, especially at Xmas. Book ahead of time too as its very busy. Haven't been for a few years so i don't know specific places to reccommend anymore. The skiing is amazing, I'm told. Shopping is quite limited, but there are lots of restaurants to choose from. Have a great time!
I have been many times. It is an excellent resort, in terms of variety of skiing, restaurants and bars, however as Purplelover says it is very expensive and the jet-lag is a killer. I went last year and was a little disappointed, but let me know if you want more specific information.