A few places I REALLY like along the Lake Superior ride. The first is Copper Harbor and the incredibly scenic/fun mountain road ride from Copper Harbor to Eagle Harbor called Brockway Mountain Drive (toad or tow vehicle only, not big rig friendly). Consider a tour of a closed copper mine while you're at it.
The next is a little known city park between Christmas and Munising. Easy/quick access right on your way, right on Lake Superior, big rig friendly with a few drive throughs. A great place to stay if you are interested in checking out Pictured Rocks. We travel spring and fall (when the kids are in school) and have never needed reservations.
Munising Tourist Park Camp Ground | Online campsite rentals in the Upper Peninsula, Michigan
Next would be a day or 2 in the area of White Fish Point with the Great Lakes ship museum, and Tahquamenon Falls. Both very unique/worthy places you won't soon forget.
Last, before dropping into the land of Trolls (people that live under the Bridge) is another city park. I was just turned on to this one a few years ago, and was hooked immediately. Can't pass anywhere nearby without spending a day or 2 now. This is right in the Soo. Some of the better campsites place you right on the St. Mary's river, within just a couple hundred yards of the lake freighters going by. These things are SO BIG they'll take your breath away the first time you see one. They aren't noisy at all, but at night there's a very subtle thrumming you can hear (or maybe feel?) - caused by the huge propellers.
Here, demand for the waterfront campsites is high. If you want one you'll need reservations well in advance for sure. Not something I would ordinarily do, but here, well worth the hassle.
Suggest you seriously consider a tour of the locks by boat too. That's something you won't forget either.
Parks and Recreation / Aune Osborn Campground
You'll want to spend at least some time in the area of the Mackinac Bridge. There's a city park on the south side that easy to get in and out of for pictures and a breath of fresh air. If you have the time, a day trip (or at least an afternoon) out to Mackinac Island would be in order! Pretty touristy, but on the way back I'm always glad I went.
From here, unless you want to bounce over to the West coast for your trip down (consider a trip over to the Sleeping Bear Dunes), you'll find the drive down the east side an easy one with some really nice state parks along the way.
That should give you an idea of what you'll miss with the short cut through Chicago....