i agree with wes
at 4 years old you can pretty much take kids anyway, depending on height restrictions etc. its when they become a bit older and know they are scared. but by then they know what they like also so it works both ways.
how about trying the tea cup and saucer ride as your magic kingdom opener?. also at typhoon lagoon there is a kids area you can hire good float jackets and in the older bit the smaller of the two big water rides is great for little uns where they go down in a ring on their own. obviously you go first or behind! plus of course the family ride where you're in a big one together. the longer solo ride is now quite quick and can be bumpy, but is still great fun.(great to see the smile/suprise on there faces.

you will find lots of things to do at each park. try to get the park guides before you go, or someone suggested get there early ,get the guide, then have 15 mins over a coffee and juice planning the day.

i'm so jealous i'm gonna book another holiday!!
trev [8D]