If I had that aged kids(or gradnkids) I would probably wait a few years until they could appreciate the roller coasters, since that is the big draw for that park. When I went a few years ago(I was 10, but I LOVE thrill rides/coasters) I loved the few rides I did go on. That's one thing, the lines are killer. That was a few years ago now, though, so I hope they improved upon fastpasses and things like that so you can bipass the lines and go straight to the fun. I didn't go on any of the kids rides, nor see any shows, but like I said above, I would probably wait until they were older and really take advantage of the high prices and let them enjoy the roller coasters, they are the best in the world!!
JMO, though!