We've done the East to West and West To East Route Across Canada on several occasions, but we do primarily boondock/dry camp.
Personally we don't drive after dusk on the Sault Ste Marie To Thunder Bay section in Northern Ontario (approx 8 hrs), lots of Moose, Bear etc on that stretch of road after dusk. Lake of the Woods is beautiful if you get chance to stop over there for a couple of days. Hubby likes fishing at Nipigon On area and we typically will boondock overnight somewhere around there. You'll also see as night starts to draw in many truck drivers pull over onto gravel large parking areas due to the activity of wildlife more than anything on this same stretch of road.
Campgrounds in and round Winnipeg, you might find this a useful resource: http://www.campscout.com/town/MB0002/