You are asking for info on a large area. I usually go up to the Bayfield, WI / Apostle Islands area a few times every summer. There's some very nice kayaking, swimming/beaches, hiking & biking opportunities around the area. It's a very fun area with lots to do.
There are some really nice state & local CG's, but without the hook ups. If you need
the full hookups (elct, wtr, swr, cbl TV), the following link to Apostle Islands Campground may be for you. Nice place, not too expensive. And a great summer area!