Cinandtim,
I think I know a place that will suit your fancy for a day or two of dry camping.
On 123 about an half of a mile west of intersection that is Paradise, there is a large parking area for the snowmobilers that is not very busy this time of year. It has trails leading off in several directions. I never traveled any of those because we were there to sleep. The only services available there are fresh air and sunlight. It is pretty level.
If you go though Paradise and go north, you pretty much have to end up at the Whitefish Point Light Station and Shipwreck Museum.
You can take 123 through Newberry to the road that will take you to Munising.
Keep track of fuel in the UP, it is not a densely populated area.
If you have time to stop at the locks on the way by, the kids will remember them "flushing" a ship.
Matt