I want to buy my nephew/godson his first compound and present it to him when he visits next month. He is 13, but on the small side..

How can I estimate what poundage he can pull back ?
How can I estimate his draw length - I can ask his mother to take some measurements and tell him it is for a jacket..but what measurements?
Which model children' s bow should I look at... I want it to be good, but he will also outgrow in short order so not too $$..
Your thoughts, experiences appreciated....
Chrisvst