There's a private, full-service campground right on Lake Macatawa called Oak Grove Resort Campgrounds. I've never been there, so don't know what it's like, but the rates seem pretty reasonable. You can check out their website at oakgroveresort.com. Might be worth a look-see. If all else fails, you might try Ionia State Recreation Area, near Ionia. It would be about 1-1/2 hours east of Holland, but they have a nice smallish lake, a very nice beach, and they appear to have some availability in August. I've camped there a couple of times, and go there fishing quite often.
2013 Eagle 266RKS
2011 Ford F-150 w/3.5L Ecoboost & H.D. Tow Package