Welcome to the Victoria forum, Travel ~
I have a question to try to clarify your question. You are on the Victoria Forum. Are you actually disembarking in Victoria, BC? I'm pretty sure you mean Vancouver. Perhaps you could confirm where you are disembarking the ship. And this will be in July?
I think you could easily spend 3 nights in Whistler which would give you 2 full days. There's enough to do there for 2 days. I would also suggest to spend your last night before your flight in Vancouver. Travelling across from Vancouver Island on the ferry on day of travel is not the best idea. So that leaves 1 night spare. I actually think you could spend that one day very well in Vancouver as you spent only 3 days pre-cruise.
If you could tell us a bit about your interests, what you like to see and do when you visit a new place. That would help pinpoint a destination that would satisfy those needs.