I would spend about 2 days in the MK and split the other 2 days between the other three parks with those ages. But, if your kids are having a great time in a park, then roll with it over park-hopping just to get to another park. Feel free to take it easy, your kids will probably enjoy some things you wouldn't even guess they would. Just don't try to overdo it, all you end up with is cranky kids, and then you end up muttering something like, "I spent ___ dollars on this vacation so you had better have fun!"
I hope you enjoy it.