With Scouts in mind, I'd suggest Punderson State Park. There is a lake there, and you can rent row boats or even a pontoon boat. It's been 7 years or more since we were there, but I wouldn't mind going back.
Another option could be the Streetsboro KOA which has a nice area for tent camping. I would call them to see how they handle groups and if you could use the tent area that is closer to the office. Don't know how that would work with your RV. It's really nice and set off from the RV area. Travel time up to Rock & Roll will be about 30 minutes, but I'd suggest avoiding prime commuting hours as the 480 can be pretty hectic.
Another option is the American Wilderness Campground (https://americanwildernesscampground.com/) in Grafton. Again, about 30 minutes or so travel time to the Cleveland attractions.
Hope you have a great trip!