Ask HN: recommended animation app for a 9 year old?

Hi All, A friend (our midwife in fact) has a son who wants to learn how to make his own animations. My knowledge of animation extends to certain jQuery effects and sprites on my old Z80 system, so I was hoping that there'd be some animation gurus on HN who could recommend a program that: - is easy enough for a nine year old to pick up - would allow him to create fun animations quickly and easily, to keep his interest levels up - either runs on MS Windows (I know, I know ...) or is a web app Thanks in advance for any recommendations ... Yours, Duncan Bayne