You want to pick out a yoyo thats easy to learn on and is cheap and will last him a while for tricks.
I would definitely not recommend a speedaholic or a psg for him, even though they are dirt cheap and fantastic yoyos they come with a very wide gap and can be hard to learn on.
I just feel like they are more suited for more advanced players.
I personally would recommend the classic,velocity or maybe even a flipside.