I don't know if you will see bears in the wild around Vancouver unless you head up towards Whistler. You will probably have better luck seeing them when you are in the Rockies.

As per the rest of your Western itinerary I would consider staying two nights in Banff if you can swing it as there is a great deal to do and see if you are based in either Lake Louis or the town of Banff. When you are in Calgary you can always do day trips to Banff if your friends have a car as it is only a bit over an hour from the western fringes of Calgary. A day trip to Drumheller and the dinosaur museum is also worth it--about 90 minutes east of Calgary.

As per Niagara Falls you certainly don't need to stop in Hamilton. There is also Go Train service from Union Station in Toronto to Niagara Falls on weekends and holidays in the summer. You might consider this as opposed to driving. In the summer the traffic between Toronto and Hamilton always seems to be worse for some reason. You might even look into taking the train and then renting a car for the day at the Falls if you are interested in seeing other sites in the region--i.e. wineries and Niagara on the Lake. Alternatively, you can also take bikes onto the train from Toronto or perhaps can find a place to rent them in Niagara. Parking can be a nightmare and a bike would be much easier. There is really nothing worth stopping at between Toronto and the Niagara region from a "must see" perspective.

I'm not very familiar with hotels in Vancouver or Toronto. Perhaps let people know what you want to do and see in both cities so that they can get an idea of what a good location for you would be.