It sounds like you want the kids to make an animated character of them selves. That is a very long and complicated process to do by scratch.
I have some video tutorials on my web site for a $50 dollar modeling program called fragmotion. It is one of the best programs to use with FPSC.(IMHO)
go to
http://www.chaosbrosfilms.com go to joe's page and you will find them there.
Another method would be to retexture an existing model using the childs photo... i believe there is a tutorial somewhere on these boards.
Try this post here
http://forum.thegamecreators.com/?m=forum_view&t=186901&b=21
gamer, lover, filmmaker