Lots of various simple dispersed "camping" locations at Double J etc just north of tiny Rothbury, MI which is maybe 35 miles north of where we live. All I've seen is dry camping/staying overnights. Very crowded lines of camping units and gob and gobs of tents or ground sleepers. However be advised that the crowd is usually more than 30,000 or even a lot more. Extremely popular! Once you are in, there's basically no leaving until it's over, so be sure you have everything you want or will need.
Just think about how many cars/vehicles a 30,000+ crowd has attending and so many stay in their vehicles or RVs right in the long jammed together lines and lines of parked vehicles with no hookups of any kind so be prepared for it. We have seen lines over 5 miles long in all 4 directions just waiting to be able enter the Double J grounds. Yes, Double J is a very big place and it fills nearly every square foot during the Electric Forest time as it's packed.
We're too old for that stuff but wasn't 50+ years ago.
A superb CC LB 4X4, GM HD Diesel, airbags, Rancho's, lots more
Lance Legend TC 11' 4", loaded including 3400 PP generator and my deluxe 2' X 7' rear porch
29 ft Carriage Carri-lite 5'er - a specially built gem
A like new '07 Sunline Solaris 26' TT