We have taken that route many times. We have stayed at Mineworkers RV Park in Sudbury, Sault Ste. Marie KOA, Wawa RV Park (nice little park), and Thunder Bay KOA.
Don't know where you are staying in Toronto but take a look at Milton Heights Campground. Very well managed, and well kept RV Park with new owners. Good access to Niagara Falls (1hour) and good public transportation into Toronto using GO train.
The trip you are going to take is a nice drive, good highways and some nice scenery. No problem with getting gas/diesel with lots of easy access pumps all along the route.
We were travelling in 40 ft 5th wheel.