Our good friend Steve Taylor at Stripey Design is a designer and developer who is both impossibly nice and talented. We're working together on a few projects we can't talk about yet but rest assured we will soon!
Well a while back he created an animation tool specifically for kids called Anithings. It's well designed, easy to use and surprisingly powerful, which is probably why it's won a bunch of awards particularly in the education space where it is hugely popular in primary schools. If you have budding storytellers in that age bracket I'd urge you to take a look, you can even try a free online demo of Anithings here. My daughter (6) and I played with the free demo over the weekend and it was so much fun I've ordered a copy.