How close you can get to the parade or castle depends n when you are going. If you're going on a day that is not blacked out to AP's, expect it to be packed.
I did DL 2 summers ago right after I got my 17-55 f/2.8 and shot 95% of the time with that. I don't think I used my longer lens at all. I did swap out a little with my Sigma 30mm f/1.4 for dark rides. There are a few more dark ride options there (Alice, Mr. Toad, Pinocchio). I also used my UWA a bit.
Can't comment on Carsland since that wasn't open then.
Have fun! I want to head east this year to see the FL Expansion. But then I think I have to get back west in 2013.
I would probably skew toward saying you won't need a long lens as much at DL, but I'm probably forgetting something. Everything there just seems smaller and closer together.