I wouldn't try doing Niagara/Toronto and Vancouver on the same trip.
But Vancouver & the Rockies yes, or Toronto & Niagara, yes.
If you do the Rockies, Canmore is about 1 hour drive west of Calgary and a good base for doing the mountains. Visit Banff while you're there, but stay in Canmore, it's cheaper; drive up the Icefield Parkway towards Jasper too. Lake Louise is very pretty, but nearby Moraine Lake is supposedly more picturesque. The Athabasca glacier is quite impressive too. If you want to park up while in the National Parks you'll need a Park Permit, which can be quite expensive.
In Vancouver itself, Stanley Park is nice; Chinatown is worth a look and the shopping in downtown is quite impressive.
En route between Canmore & Vancouver is Kamloops, it can get quite warm there in the summer (39decC in August while we were there), quite popular with the 'freeride' crowd. Okanaga valley is Canada's vineyard. The high route from Kamloops to Vancouver can be almost desert-like scrub in places, more like you'd imagine Nevada/California to be…
And don't be disappointed if you don't see too much wildlife. We saw 1 elk, umpteen magpies, squirrels, rabbits, chipmunks etc, half a dozen eagles, but not a single moose, bear, wolf, coyote, cougar or anything else remotely dangerous in 2 weeks. Oh, and some semi-tame raccoons in Stanley Park
Lake Louise is about an hour further from Canmore; Vancouver is 9 hours the 'quick' way or 11 hours if you take the high route
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