Michigan has a lot of very good rv resort and state and private campground. Just do a search and pick the one that meets your need. My wife and I like Wild Cherry on Grand Travers Bay www.wildcherryresort.com
A very good place to spend a few day, with everything you need is their in and around Traverse City. A trip in the slow lane up 31 to Torch Lake, and Charlevoix is always good. Mackinac City has Michilirnackinca State Historical Park. Wildness State Park is right on the Lake Michigan with beach with sand. I would check to see if the park has a site your rig will fit into. Myself, I like St. Ignace and the trip acrosse the MACKINAW BRIDGE is the highlight, Just hope the wind is not blowing. There are more very good campgrounds in and around St. Ignace. A trip to UP would not be complete with out a stop a Tahaquemenon Fall State Parks or Picture Rock Nalional Lakeshore is not a bad place to spend a few day, There are some nice beachs there, where the water is clear and cold!!! The boat ride out of Picture Rock is a must do, the one at sunset is best one. I have just name a few places the wife and I like. Injoy your trip thur Michigan and take your time, You would not want to miss anything.