I am from Manitoba, so will give local info.
There is a really nice campground at Falcon Lake, just over the Ontario/Manitoba border. There are actually two campgrounds, but the one closest to the townsite is the most convenient.
There is a Flying J truck stop one mile west of Winnipeg on the TC, and I am pretty sure you could stop there for the night. Or about another 5 miles further west, there is a nice little KOA on the south side of the highway, right by the river. Although with all of the snow we have had this winter, it might flood and they could still be cleaning up when you pull through.
In Saskatchewan, we usually stop in MooseJaw. There is a really good private campground just off the highway. I think it is at the second exit.
Further west, the campground at Cypress Hills Provincial Park, just south of Maple Creek, is very wooded and quiet. There is another campground in the same park on the Alberta side, but don't stay there. Don't get me started!
Once you get into BC, the options are limitless! I could recommend a whole bunch of places, but you know what you are interested in. Just do lots of internet searches.