My daughter is about 36 inches. We originally didn't get a two park pass because there wasn't much to do there for her. We have since upgraded though. We go for a couple of hours here and there.
Things she can do
shows:
Muppet 3D
Who wants to be a millionaire (she likes pushing the buttons, but get's antsy after a while)
Animation building (haven't had a chance to get there yet)
goofy's beach party bash (it's outside so if it's cold you might not want to sit for it)
electrical parade
eureka
luminaria
Tough to be a bug
there are also other shows, but I haven't gotten a chance to see them yet.
Things she can ride
King triton (merry go round)
golden zypher
sun wheel
superstar limo
She isn't tall enough for jumping jellyfish or soarin.
She likes to play in the farm area (they've got water, so be prepared to get wet)
the little play ship (more water, but getting wet is not a must)
grizzle trail. There are slides, the tire things and rock climbing you have to be taller, but they can do the slides and tunnel and stuff.
as someone else said if it's not going to cost you too much more it might be worth it, especially if you can go in for a little while, then go to DL, but if your kids are expecting to go on lots of rides it's not worth it. One thing we do is we go get a child switch for a ride, and then one takes her to a play area or show while other rides, then we switch, so she get's to play, and we get to ride.