I took the North Lakes route in the summer of 2012. I camped the whole way too. The Interstate Park south of St. Croix Falls, WI has beautiful grassy sites, with great showers for no extra charge and some historic interest. There is a great, inexpensive municipal campground in Birchwood, WI (great shower for 25 cents). I camped at Day Lake outside Clam Lake, WI in a nearly deserted but perfectly nice NFS campground (no showers, but a lake to jump in). Big Lake Campground short of Boulder Junction, WI was great with a lot of friendly people (no showers, but a lake to jump in). The campground at Pentoga Park on Chicaugon Lake near Gaastra, MI was expensive and very lively (circus atmosphere), but also nice--they have an ice cream shop in the campground (good showers). The campground in Escanaba, MI at the Upper Peninsula State Fair was adequate and inexpensive (reasonable showers). The Milakokia Lake State Forest Campground near Blaney Park, MI has no showers, but has a lake to swim in. Straits State Park in St. Ignace has one of the most beautiful campgrounds I've stayed in with a view of the Strait and bridge. The municipal campground in Petoskey (Magnus Park) is quite nice. Whitewater Township Park, several miles outside Williamsburg, requires you to ride a sandy road to get there, but it's nice although expensive. Old Grade Campground (USFS) ten miles west of Luther, MI is primitive but cheap.
I did not find traffic a problem on this route. I see no reason to deviate from the ACA route. Highway 2 across the UP can be a bit busy (if you don't take the ferry across Lake Michigan), but there are few alternatives.
Seems to me that the ACA route does indeed follow Lake Michigan as much as possible, at least as far as Traverse City. I'm not sure why it goes inland after that.