In Toronto there is a no frills campground, that does offer electricity, water and a dump station, at about $40 a night. It’s the Glen Rouge Campground. TRCA Reservation Service
You won’t find a better location for visiting the city.
In the Kingston/1000 Islands area I would recommend the 1000 Islands/Ivy Lea KOA. If you have the time I would recommend any of; Fort Henry, Canada’s Penitentiary Museum, walking around/dining downtown Kingston, a 1000 Island Cruise (Gananoque Boat line is the best) and Upper Canada Village. I believe if you purchase a ticket to either Fort Henry or Upper Canada Village, it also gets you into both (although, it would take 2 days, because of time to tour/distance between them).
The Montreal South KOA, is close for visiting the city. Walking around the Old Port of Montreal is nice in the summer. There is also a Biodome, which offers several attractions for kids. There are also a few water parks in the area. We have been to the Granby Zoo and enjoyed it. This is a smaller zoo and water park, all at the one location. Friends go each summer, camp and go to the water park at Ski Bromont.
Lake George is a great area to visit. If you are there and have time, look at going to the rodeo, the Painted Pony Rodeo. They usually have shows on Wed, Fri and Saturday nights (don’t bother with their BBQ).
We have also been to Hershey and enjoyed the amusement park and Hershey's Chocolate World. We ate at a good Italian restaurant, Fennici's in Hershey.