If you have a child that doesn't like the dark I'd beware of the following rides:
Dinosaur!
Expedition Everest
Tough to Be a Bug (for sure!)
Haunted Mansion
Tower of Terror
My DS (then 5) laughed on the Tower of Terror, went on Expedition Everest 3 times in a row, but couldn't get out of Tough to Be a Bug fast enough. So really, it's going to depend on the personality of the child.
It probably would help to check uTube out just to get an idea of the ride but sometimes you have to just try things out.
Good luck and I hope you have a safe a magical trip!