eehh... maybe it is better to loose some weight first, before lifting it... He is (in my opinion) to young to do serious weightlifting. His body is at a crucial point (being 13 and all) of developing. Lifting weights to young is just not good for the bonestructure and stuff. (don't exactly how to put it down in english, sorry, but you get my drift i guess).

My first comment is a rather serious one. He's big for a 13 year old. Loose weight by doing a sport in which you have to move! Like boxing or soccer or whatever! Then when he's about 15-16 he can start thinking about a little weightlifting...

But like i said, that's just my opinion.....