Darren,
I fished the Bow near Canmore a couple of years back with a guide called Jim Dykstra -
http://www.flyfishingbanff.com/
He was a top bloke with a good knowledge of the Bow thereabouts. Don't forget that the Bow is more famous for its water away downstream. Up near Banff, it runs hard with that crappy glacial milky tinge for a good part of the summer and we had to employ some down and dirty tactics to find fish. Even then, we got plagued by whitefish which was ok by me, but the locals hate them!
There are plenty of lakes in the Banff area too, but you could do with a tube to fish them well. I caught a few at Jackson lake a few miles up the road.
I think Jasper is a bit thin on the fishing front, but the coast mountains are much better. There is a hell of a lot of good fishing in the whistler area.
On Vancouver, I briefly fished the Cowichan River - very low water, very spooky fish, but good access via a fisherman's trail. I believe the Campbell and Nimpkish are also worth a try but it's a big island and some travelling could be involved. Again, loads of lakes; I had a few from one called MacArthur.
I'm sure you'll have a great time, the place is magical!
Matt