well speaking for my 2 yr old son who is a cars FANATIC. Im not kidding, we have every single car made in every form (some even 2 and 3 of each), the shake cars, the minis, the regular diecast, the big talking one, etc, i could go on and on. He would like to see more cars things. He is going for his first trip and we told him about queen (thats what he calls him) and mater being their and keeps saying, and sally, and doc too. and bessie and mone (ramone) too. SO maybe have a radiator springs garage area with all the cars, over in the pixar section.
for DD5 more HM, HSM, Camp Rock, meet and greets. Like look a likes like they did with kim possible. Maybe even some kind of show or play that you sit at, not just the HSM parade. Or interactive area where the kids can pretend they are on the scene of the show/movie.
and for me, I would like the skywalk chair lift at MK to come back. I rem that as a kid and loved it.