Lake Superior circle tour

Did a circle of the lake in August 2008 with 2 other units and saw 54 waterfalls in 17 days. Have a great trip.

There are not a huge number of campgrounds in the upper peninsula of Michigan and that particular time frame is one of the busiest as black fly season is finished.
I would recommend reservations where you you can, and for the rest, when you have determined where you plan on stopping for the night, call earlier in the day to get a spot.
It is a truly beautiful trip. We spend the mo the of August in Michigan's Upper Peninsula. Post when you're around and we'll see if you're near!

I can't speak to the Ontario side, but...

When you get to Minnesota (beautiful area with many waterfalls) the state park CGs do tend to be full. You definitely want to spend some time in this area, and reservations are recommended.

Around the Michigan part, I have gotten sites on the spur of the moment at many locations. The west unit (rustic) of Porcupine Mountains SP doesn't get many campers, if you can manage no hookups for a night and like peace and quiet.

I would say so as many people are on vacation during this period, especially the last two weeks of July and the first two of August.