We have stayed at Platte river Federal forest and it has been great. Clean restrooms and everything you would want. The drive is good to the park but there are other things in the area that you will want to see. FishTown, wineries, Glen Arbor, Glen Haven and the Pierce Stocking drive through the dunes.
I would never go there without having a vehicle since it is so much more than just a pile of sand.
Have fun and welcome to Michigan.
The Empire Asparagus Festival is also in May and in the area. https://www.everfest.com/e/empire-asparagus-festival-empire-mi