There is a company that delivers groceries to your cabin/hotel/room whatever so that It is already there when you arrive. I did it..amazing.. Had food, booze, and cigars(for rolling up one of BC's major exports) already stocked in my place.. Not the cheapest route..but if you dont mind paying a lil extra, i highly reccomend it.
I cant remember exactly which company I went through..but here is one I found
Grocery Delivery in Whistler Resort by Creekside Market - Whistler Grocery Store - Deliver Groceries To Your Accommodation Rental
They leave a reciept so you know what everything costed..we split it 5 ways and it was perfect.. food/booze lasted us 5 days for around 60$ per person