We always stay at Mackinaw Mill Creek Campground in Mackinaw City. It is right along the water with Mackiaw Island and Mackinac Bridge in view. Not all sites are along the water. It's a large campground, but July is peak. Call and make reservations NOW.
There is also a State Park Campground in St. Ignace, north of the bridge.
You will thoroughly enjoy exploring the area....about an hour north of the bridge is the Soo Locks at Sault Ste Marie. They are interesting to see and you can take a very interesting boat tour and lock through the locks themselves.
โLight hearted I take to the open roadโฆ Healthy, free, the world before meโฆ The long brown path before me leading me wherever I choose.โ - Walt Whitman