Hi Lisa,
I'm really glad that you have made such a positive connection on this forum!
If your son likes "Princess Mononoke" (what good taste he has!), I would also recommend other work by the Japanese director Miyazaki - perhaps the recent "Spirited Away"? Also, I would definitely recommend "The Iron Giant" - it is another very touching, animated family film, also with an inspiring socio-cultural and environmental message. Unfortunately it just didn't get the marketing from Warner Bros. the year it was released but it's an excellent film all the same - a "wee gem of a fillum" as we would say in Belfast!
If I can think of any others I'll let you know...
best wishes
Ingrid :0)