for beginner...anything willl work..try to get something heightwise around his chin area...then for brand to get...it really depends on how much you want to spend. a good brand is always burton...i just got a new board this year...(last years Burton: DOMINANT 156)
can't wait till ride it...besides burton you can check out. Forum, M3, Ride, K2, Salomon, GNU, NW. basically just dont go for a board that is really heavy.
starting off it really doesnt matter...hes not actually going to be carving or anything serious like that...he can start off with a pretty crappy board and see how he likes it...basically like any sport...its 90% skills 10% equipment...or around there.