Choo Choo Trains and kids just go together!
This is perhaps the best value for younger-aged children ever! It is an amazing park with trains for the kids to ride and real trains to look at. Plus toy trains, swing sets, rides, and a sort of museum. NO COST to enter the park... and the rides / food are very reasonably priced. I bring my girls (9,6) here a few times a year.
In the summer they have live concerts in the evenings for free too.