...I would take your 4 year old to Seaworld. The only thing his height will allow him to do is Seuss Landing in IOA and the Nick Studios in Universal. There's a cool Barney show at Universal also, but you'll have to decide if you want to spend the money on just a few things between two parks. I could be missing a couple of things, but as I remember, my 7 year old neice missed height requirements on about 4 rides. SHE WAS NOT HAPPY!!
Go to Seaworld and give your 4 year old about 3 more years so he or she can really enjoy the Studios.
IT'S ALL ABOUT DISNEY!!
REMEMBER THE MAGIC!!!
TTFN...TA TA FOR NOW