I camped on the island two years back around mid August. The weather was pretty miserable for most of our stay, with heavy rain and winds. When we were able to do some fishing we mostly fished for LM bass around docks and boat houses. As expected, 4" or 5" Senkos wacky rigged were consistent producers. We also found LM bass in the numerous little bays off of the river flows. They were consistently on the slow water side of the seam that met current. Pike could be found just about anywhere and would hit spinner baits and inline spinners. We tried to fish for SM bass in areas that showed current and structure, but it was tough because of boat traffic and rough water due to the bad weather.
Personally I think the area is great, the scenery is incredible and there is a lot to do in that area. I didnt like being that close to the boarder line, and the area has to much tourist activity for my taste when im on a fishing trip.
Last year we stayed around 15 miles farther down river and the fishing was great and there was a lot less tourist activity. We also had over 3 miles of fishable water from the US shore until we hit the boarder line with Canada. I am headed back up on June 18th for a week.
Good luck, Tony