RE: Draw Length
Well if his bow is within the last im going to say 10years of production. It make be possible to get an extra inch out of the bow by just adjusting the cam. Your local bow shop can do this very quickly and should only charge you a few bucks 5-10max. As far as arrows, they should cut them for free and insert them if you purchase new ones. You can gestimate by buying some carbon expresses at walmart and getting very close to the length needed. These arrows run 3-9dollars a piece at walmart. A cheap dozen may cost you 50-75 bucks at the bow shop Remember I said cheap.
On seperate note, give yourself a pat on the back for helping a young man out. Father figures are the most important part of a boys life growing up. And it is good for someone to try and guide him, even if it is just a little bit.
Hope this helps, dont be afraid of the local bow shop, adjusting the length is fairly easy with in about an inch. Say 29 to 30. If the bow allows for it. You can also get away with a long string loop put on yourself will give him a little more length to help.