We had dinner there last week. I have 2 DDs - 6 and 9.
It is a very fun environment. Some servers are more "lively" than others. They have a horse race where all the kids (who choose to participate) ride around the dining room on stick horses (like a broomstick with a horse's head on it). If anyone at you table asks for ketchup, a server will scream "ketchup" as loud as they can, and you will be given just about every bottle of ketchup in the restaurant. It then becomes your job to deliver them to the next person requesting ketchup. It gets to be pretty fun.
Some servers are more "playful" than others. I think they try to get a read off the customers to see how much they'll play along. My DDs had a wonderful time. The one thing I didn't like was the limited menu choices. Not a lot of options if you're not a big meat eater. My DH on the other hand was in hog heaven - they have bottomless milk shakes there, and you can change flavors with each refil.
Enjoy!