Waldameer amusement park has a variety of classic rides that are geared toward kids up to about age 14. I just took a group of six 13-year-old girls from Pittsburgh and they enjoyed it, although most of them would typically ride larger roller coasters. We combined riding with swimming at Water World where there is a hot tub and several large water slides. The nice part for us was that it was not crowded at all (cooler day with threat of rain kept people away I suppose). But Waldameer is known for being a smaller sized park and that makes it easy to navigate. It is smaller than Kennywood in Pittsburgh--but Kennywood doesn't have a water park, so this was something different.
They allow guests to bring coolers with food so you can easily take the family and not spend a ton of money on meals. Food is typical park fare-burgers, dogs, funnel cakes, fries, ice cream, etc. Picnic tables are available. Parking is free.
This is one of the few parks where you can enter for free as a non-rider, or pay-as-you-go for rides if you just want a few. Check out the Wally discount card for this option. You do need a water park wristband to enter Water World, even as a non-swimmer.
If you want to make a longer day of your visit, stop at Presque Isle park and play on the shores of Lake Erie, or just go for a ride down the Presque Isle peninsula.