I'm a bit partial to western Michigan and the Lake Michigan shoreline. There are some very nice small towns north from South Haven: Saugatuck, Holland, Grand Haven, Ludington, Manistee, the Leelanau Peninsula in very northwest Michigan (Sleeping Bear Dunes Nat'l Lakeshore), Traverse City, Petoskey and right on up to the Mackinac Bridge.
In South Haven you'll find a fairly new FHU campground called Sunny Brook RV Resort. If you like blueberries early July is the time for them in the South Haven area. Downtown SH is very nice and the Lake Michigan beaches there are great. A visit to the small towns of Saugatuck & Douglas will give you that tourist/artsy stuff.
http://www.rvparkreviews.com/regions/michigan/south-haven/sunny-brook-rv-resortUp in Holland you'll find a great beach at the state park, but if you prefer FHUs just down the road is Oak Grove Campground. Downtown Holland is nice and while it's not the season for tulips it is called the "Tulip City" with a strong Dutch heritage along with a real Dutch windmill.
http://www.rvparkreviews.com/regions/michigan/holland/oak-grove-campground-resortFurther north along the lakeshore is Silver Lake near a small town called Mears (near Hart, MI). We stayed in very nice FHU RV resort called Silver Creek RV Resort. The large dunes (dune buggy rides) and Lake Michigan are the big draw here, but there are other things in the area to visit. Cherries are also in season along the lakeshore.
http://www.rvparkreviews.com/regions/michigan/mears/silver-creek-rv-resortLudington is a very busy summer town along the lakeshore. Some neighbors stay the month of July in a FHU campground there called Poncho's Pond TV Park. It's highly rated with over 250 sites.
http://www.rvparkreviews.com/regions/michigan/ludington/ponchos-pond-rv-parkFurther north is Manistee. There is a FHU campground at the Little River Casino. From there you can take a day trip or two north to Sleeping Bear Nat'l Lakeshore near Glen Harbor (follow M-22 from the casino north-beautiful ride). A bit further north is the Leelanau Peninsula. It's very pretty in this area with lots of cherry farms, wineries, and cute little towns. I'm not familiar with any FHU campgrounds in this area though. And would stay at the casino or check over near Traverse City for a FHU park. I know there are some, but I've never stayed in any of them.
http://www.rvparkreviews.com/regions/michigan/manistee/little-river-casino-resortIf you don't want to visit the west side of the state (the most beautiful side IMHO) there is the Henry Ford Museum and Greenfield Village in Dearborn west of Detroit.
Have a nice trip.