Three places come to mind. They may be too young yet for Wright-Patterson Air Force museum, but the hanger with the rockets may relate to them. The Ohio Caverns in West Liberty should interest them. Roscoe Village in Coshocton is interesting, but more of tourist
thing with mostly shops, some history of canal life. COSI in Columbus would thrill them. These are all day trips from Marion. We usually do trips like these with our grandkids outside of camping season. Going to Dayton was fun for 2 boys, 8 and 12, because we stayed overnight at hotel with a pool. They both enjoyed the museum, also. MAPS air museum is Canton looks interesting, never been there and I live within an hour of it. Life is so unfair, why can't we go straight to the grandkids without having to have the kids first?