I had never heard of Quebec City until recently when I saw a picture of it similar to this one. It's definitely on my radar now!I know this doesn't align with most of your options, but since you have Vancouver as a summer but not tropical option - I suggest Montreal, Quebec and maybe also Quebec City. I haven't been but it seems from pictures etc that it would be like sneaking into old Europe without as long of a flight, possibly cheaper. Here is a google maps streetview chosen at random in the old part of the City:
https://www.google.com/maps/@45.504...4!1sNfajvTXhC3g1exDnkgacLQ!2e0!7i13312!8i6656
Also a vote for summer in Iceland. I've wanted to go to Iceland for a long time - wish I would have before it was cool!
My 2 cents: Curacao would be my pick just based on the pictures in that link and the fact that it's less known and looks like a neat experience. I think Banff and Iceland are overdone right now. I'm sure they are gorgeous and fun places to visit but my sister and I had a running joke this summer of texting each other every time we saw another Banff post on Facebook. There were so many! Might be best to wait a couple of years and hope that the interest in those places dies down a little.