They may enjoy the Newport Aquarium in Newport, KY, just across the river from Great American Ballpark. Kings Island Amusement park would be great but doesn't open until April 27th. It sounds they are big baseball fans so the Reds Hall of Fame and Musuem would be a fantastic attraction but I wouldn't recommend going on game day as it's pretty crowded. Reds fan or not, the Reds Hall of Fame is just fantastic.