It shouldn't be all that hard to do. I think that technically, you have somewhere up to three months to vacation in canada if you'd like. I'd just tell the canadians that you're heading up to squamish for a week of climbing, then when you are coming back to the states months later, tell 'em you were rock climbing for 2 months (I don't know if the canadians and americans share their information, somehow I doubt it, canada hates us) and you should be set.