State Parks close to the Straits area we prefer are Burt Lake SP, Wilderness SP, Petoskey SP can be ok too and Cheboygan SP is just ok for an overnighter on the south side. Straits SP on the north side is excellent too and we like the lower section to the left or right that is right on the lake shore.
We like Foley Creek National Forest CG just north of St Ignace too as it gorgeous and real camping in real woods and nature. We are truely self contained but some want or demand hookups and there's none at Foley Creek. The huge Casino on the northside of St Ignace also has a CG with hookups as it's cheap but it's around the edge of the aux parking overflow lot.
We're not much fans of private CG's most anywhere as most are just glorified parking lots crammed in a small piece of land and are a lousy bang for the buck overall. Like having 6 lbs of ____ in a 3 lb bag! Mackinaw Mill Creek is a very large CG both in site numbers and land area and we avoid their crowded together tiny site Bridge View area also as there are so many other great sites to be had. Ironic that they built the Bridge View section for MH's mainly and so many avoid it because of the tiny site sizes. If they eliminated every other site it would be a good section like the others. They have plenty of good land to move the lost sites to so they'd have the same total number of sites yet. Overall, it's a very good CG for a privately owned one.