Last year when we went to get on the train to conservation station, they picked my kids to be engineers. They got to sit up front for a few minutes with the engineer and he told them how the Engine worked and they got to sound the steam whistle. Not a real big dream, but DD loved it.
Later in the week, they were picked a RRC in Hollywood Studios to be "Junior Valets" They each got a red vest to wear and directed the passengers to the exits from the ride. The CMs made a really big deal over them, and after they both got a few turns, they got to go on a few times without waiting in line, by going through the "back hall" from the unloading area to the loading area. They also got to pick their seats (which of course, were the front ones!) Again, not a real big dream, but it really made them feel special.