Well, I took my then four year old.
As for USF..
As for two, there are some really interesting things depending on height/fear tolerance.
ET Adventure may work, if they aren't too afraid of the dark... the entrance is set up like a woods. If you go in with him, and say, hey we're going for a walk in the woods.. they will follow your lead..
The Barney show would work for him as well
The Curious George Playland will be great/same with the Fievel Playland. Be prepared to stay for hours!
As for Jimmy Neutron.. if it is set up the same way as Hanna Barbera.. (same general structure/set up) they may enjoy that.
Obviously he would be too small for MIB.. unless you have a 40 inch two year old! (I've seen some huge kids..mine were, but thats a little too BIG!)
Jaws.. well could be a hit or miss... depends on fear tolerance, and other things.. there are gun noises, and of course JAWS pops up.. so you wouldn't want to put him on the end! I've seen little one on JAWS fine, and I've also seen older kids screaming.. its all up to the kid I guess.
As for the shows.. Wild West is funny, but can be loud, and Animal Planet is fun.. and definetely in his age group. Never got to see Beetlejuice so I can't say on that one. Barney show is fun as well, and there was a meet and greet with Barney at the end
Shrek could be fun as well, but I'm not sure if you will be there when it is opening. Again, don't know the height requirements or anythign like that as well..
As for IOA..
You have Suess Landing.. everything and anything is fantastic for a two year old. Carousseel.. Cat in the Hat, and One Fish Two fish are amazing fun rides.
As for the other lands... they could do Storm Force (I think--check the height requirements) in Marvel Super Hero. If it is a boy, they will love to see Spiderman driving along in the little parade in the street.
They might be able to tolerate the Sinbad show, but Posiedons Fury could be iffy.. I've seen small kids in it, some cry, some think its cool.
As for Cartoon Lagoon, they could play on Me Ship the Olive with you.