One quick fix for kids who might get startled during the show is to have them take off the 3D glasses (for a while, anyway).
All of the "coming out of the screen" EFX (like the snake) become flat and a bit out-of-focus without the glasses on.
Also a set of noise-reducing ear-plugs (or just some cotton balls) placed in the ears of each child is a good idea on any attraction that has LOUD NOISES (like ALL of the 3D films, Dinosaur, Fantasmic!, Wishes, etc.) can help lower the anxiety level.