State Park campgrounds hold a small number of sites open on a first-come first served basis, but it's risky, especially on a Friday. Thursdays you can usually get a spot.
We know nothing about the Barry County fairgrounds.
We have personally stayed at:
Conestoga Grand River Campground in Coopersville (1/2 way between Grand Rapids and the lake) Phone 616-837-6323.
Wabasis Lake Park, a County park about 1/2 hour northeast of Grand Rapids. Phone 616-691-8056.
People visiting have stayed at:
Grand Rogue Campground, just north of Grand Rapids. Phone 616-361-1053.
Woodchip RV Park, southwest of Grand Rapids. Phone 616-878-9050.
Other places to try:
Yogi Bear's Jellystone Park in Grand Haven. Phone 616-842-9395. We've camped there with a group; it wouldn't be our first choice.
Duke Creek Campground in Cedar Springs. Phone 616-696-2115. (No personal experience)
Lakeside Camp Park in Cedar Springs. Phone 616-696-1735. This is a former KOA right next to the 131 freeway; no shade.
Will send a PM with our address and phone number. We'd like to see Oxygen
if you have the time! Drive carefully.