I imagine that the 12 year old is going to be a cub. I run a live
Werewolf game and have a 14 year old (again a son of one of the
players) who I allow to play in the downtime games but not the main
game.

I created his character for him which may be a good idea for yourself
to do as it allows you to create an easily playable character that
works within the game and allows the player to concentrate on specific
and easy areas in the game such as a Homid Children of Gaia Ahroun,
able to fight but also good as a back up healer when you need one.
Also means he gets to take part in the talking stuff and his non-
biased reaction to the Fera could easily be explained.

James