I'm originally from Cedarville, and the wife is from Hessel. And like PJOJeep, we still go back in the summers to visit family. Not sure the age of your son, but there are a lot of neat places across the Yoop. Tahquamenon Falls (nice campground). If you come across southern UP you have Lake Kitch-iti-kipi
Link with the Hiawatha National Forest to the north. Soo Locks is a great visit if you come across north UP. If you make it up to Munising, Pictured Rocks is a nice stop.
Make sure you stop for a pasty and a Vernors and meet some of the awesome Yoopers.
Not sure about cell service. Unless things have changed, they are not something to rely on. If you have a GPS I'd def use it. Along with
VVmapping.
Here is another link that might help with some trails.
www.fishweb.com
Enjoy and let us know how it goes. The family and I will be back in the UP end of June thru the Fourth.