Sounds like a great trip!
We've found the best deals from Avis, and we always Google coupon codes to use before purchasing online (another discount if you buy online).
If you're looking for activities to do Groupon sometimes has really good deals on tours and activities and stuff. Banff is my favourite place, I recommend getting in a hike (tourist office can recommend one that matches your goals), going to the hot springs (pool), and getting a beer at Banff Brewing :-) They have a decent happy hour too.
I'm not sure what route you'll take, but check out Lussier Hot Springs (natural pools) if you happen to pass by!