Splash Harbor? Castaway bay? The zoo? There’s a kids museum in Mansfield.
We did that for my oldests second birthday. We went to the mighty children's museum in Chillicothe. https://www.mightymuseum.org/about Cincinnati also has lots of fun things. There's the zoo, the museum center, the aquarium, the art museum to name a few.
if you like camping, we do a jellystone campground trip every year. They have a couple different ones in Ohio. Very kid friendly with activities planned for the kids.