You're youngest is a peanut, huh? You might be doing some baby swapping and/or splitting up and one of you doing some rides with the older ones while one does something with the younger ones. I have 4 kids and we have to do a lot of that anywhere we go...
My son was 40" tall last April and is now 42" tall. Last year he could do most everything at Universal Studios, with the exception of Men in Black. It really depends on how easily your children scare. He was tall enough to sit in the moving seats at Jimmy Neutron (they have other seats for shorter kids), but was scared and thought he was really in the ocean. We went again last month and he loved it. Shrek is wonderful, but Jake was scared last month, but will more than likely be fine when we go in April.
Islands of Adventure will be a little harder. Last month he could do all the rides except for Ripsaw Falls (it was closed, anyway), the big coasters, and Dr Doom. Last April he also wasn't able to do the Popeye raft ride and Jurassic Park. If your 3yo isn't yet 40" with shoes on then he/she won't be able to do Spiderman, either. Ask outside of every ride about the baby swap. I wouldn't want your older children to miss out on Spiderman or some of the other rides because one child is too small.
There are plenty of things for the whole family to do together. Suess Landing in IoA is very good and there is a small roller coaster in each park that you can all go on. Also, don't forget Barney in Universal Studios. The Curious George water area and the balls are a lot of fun. Either bring extra clothes or have the kids wear swimsuits.
I know that I'm forgetting things, so if you think of anything, ask away!
T&B
