Splash Harbor? Castaway bay? The zoo? There’s a kids museum in Mansfield.
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.
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.