So, you dont really want a one boot does all solution imo.
Get yourself a warm winter boot and a pair of boot that will let you do whatever hikes you fancy in teh summer.
I'm guessing you're not going to be doing any multi day hikes in teh summer.. as you're on a bike forum, so you would probably tend to ride into locations.
Sure Whistler has some awesoem hikes (Rainbow, Singing Pass, Rubble creek/Black Tusk/Garibaldi Lake..Squamish has Elfin Lakes, Stauamus Chief etc) but none of these are huge overnighters and don't really need much more than a decent hiking shoe that you can also wear in teh spring/fall as your every day footwear.
I brough my DofE hiking boots, never wore them.. brought some goretex salomon hiking boots.. waste of $$, I ended up just wearing goretex shoes in the winter anyway.
My suggestion, unless I'm missing something about your planned activities would be:
To be honest though, turn up in what you are wearing as a casual shoe right now (unless you're a brown leather boat shoe kind of guy or are into winkle pickers) and figure out what your needs are when you get here.
Whistler has a wealth of shops, and Vancouver has MEC