The first thing that we always do with the children is to take them through a series of clips from the last 100 years of animation, from James Stuart Blackton's Enchanted Drawings, all the way through to Avatar. I think that it's only through understanding where animation has come from, and seeing some of the early experiments and breakthroughs that a proper understanding and respect for the medium is born.
I remember my first experiments with animation. We did a thaumatrope in class when I was about 9. A thaumatrope is simple a disc with string attached. On one side is a drawing of a bird (for example) and on the other side is a drawing of a cage. When the string is pulled and the disc is spun, it appears as though the bird is in the cage. This is because of persistence of vision; a flaw with the human eye which causes it to retain an image for a fraction of a second longer than it sees it. It is because of this flaw that both film and animation can work.
Needless to say, the thaumatrope got me hooked, and I spend all of that night making my bird sit inside the cage, before moving on t0 Zeotropes and Phenakistiscopes and (slightly easier to spell) flipbooks.
So, for kids who are budding animators, and for parents who are desperate to give their offspring something to do on a rainy day, here is a template for a thaumatrope that you can print (on to card) and make in a few minutes...
And for anyone out there who is no longer impressed by spinning disc (shame on you), I cannot recommend Dick Balzer's website highly enough. It contains information and images of all of the pre-animation animation toys, such as Praxinoscopes, Tachyscopes, Phenakistiscopes and other such dyslexic nightmares.