I am not very familiar with the Wisconsin side of the lake as we have spent very little time there. However, all along the Michigan coastline there are a myriad of choices, depending on what you are looking for.
Apparently you already know about Ludington State Park. Make reservations very early as it is a very popular park. Sites are electric only with a very adequate dump station near the entrance for dumping and fresh water fill. There are also some very nice commercial parks in the Ludington area.
If you are inclined to stay in the Manistee area I would recommend the RV park at Little River Casino for a night, Very nice campground with full hookups including cable tv and wifi, but not as much for the kids to do. Very reasonably priced with access to the motel pool and of course the casino and restaurants.
Traverse City State Park is also very nicely situated with a beach area on the east arm of Traverse Bay. Again a very popular park with reservations needed well in advance.
Petoskey State Park is located on the extreme east end of Little Traverse Bay just north of Petoskey. Reservations needed here also. There is also a KOA north of Petoskey along US 31 that is extremely nice. full hookups and lots for the kids to keep entertained. This is a great home base area to explore the area all the way up to the bridge and Mackinaw City.
On the UP side of the bridge is Straits State Park. Typical state park with fantastic views of the bridge. Easy access to St. Ignace and ferries to Mackinaw island.
Of course there are lots of National Forest campground along the entire route if that strikes your fancy.
Just west of Escanaba is the town of Harris. There is a casino there with a very nice RV park set away from the casino in the woods. There is shuttle access to the casino and hotel. I understand they now have a very nice golf course there too.
There are so many choices it's hard to pick just a few. If you have any questions about a specific area fell free to pm.
Tom & Barb
'07 Winnebago Voyage 35L
Workhorse W22 Chassis