There's a few private campground south of Mackinaw City. You can tent camp on Mackinac Island but no RV. West of the city about 20 mins is a state campground.
In St. Ignace (across the straights) there's a state campground right off the expressway, and a few few private ones North of town.
No idea on the fishing stuff, sorry, not my scene.
2013 KZ Sportsmen Classic 200, 20 ft TT
2020 RAM 1500, 5.7 4x4, 8 speed