Ibanez is definitely something to look into.
Realistically, you may want to buy him a full sized guitar if you think he's going to stick with it... it may save you from having to buy another guitar once he outgrows the smaller one.
Ibanez has some very nice selections and their necks are nice and easy. As far as I know, they're more of a rock/metal guitarist's pick, so you should keep that in mind if your son is aiming more for a blues type style, in which case you might be better off getting him a strat.
Check out
Musician's Friend - Electric Guitars
(sorted by best selling)
Browse around and see if you and your son are interested in any of the guitars there. The user reviews are invaluable for getting a good basis of user opinion on your options before you go into a shop to audition them.
Good luck.