For Ontario Provincial Parks you can get information on park location, site availability, etc on Welcome to Ontario Parks
With respect to Ontario Parks I have the most experience with those in the southern part of the province. The driving distance across Ontario from the Quebec to Manitoba border exceeds 2100 km (1300 miles). There may be some Canadian Airstreamers who can give you some suggestions on parks on the TransCanada hwy north of Lake Superior.
In southern Ontario I would recommend Algonquin Park(great hiking trails & canoe routes, an interesting Visitor Centre and a Logging Museum). Bon Echo Park and Killarney Park are very scenic (Killarney is out of the way and does not offer electrical sites but it is exceptionally beautiful.)
Other great places to visit...check out Kingston. It is a beautiful city on Lake Ontario near the St. Lawrence River. Fort Henry overlooking the city is worth a visit. I once served in the Fort Henry Guard which represents the British Army of the 1860 era. East of Kingston there is the Thousand Island region on the St. Lawrence and there are campgrounds operated by the St. Lawrence Parks commission.
Autumn is particularily scenic at the parks I have mentioned (and they are much less busy!) If you make plans for an excursion through Ontario let me know the time of year you will be through and where you will enter and exit the province. That woudl make a difference in what I would recommend.