I have bought a MBP for my two oldest children. However, those were purchased as graduation gifts and intended as the machines they will study with and use through their college years. I figured it was the best investment I could make for technology to send them off to school with (after verifying with the school that Mac's were ok for their programs).
My kids get lesser machines to use at home. Not one of them has a requirement that couldn't be fulfilled with a much lower cost computer. I don't permit braggin rights to be part of any of their requirements and unless they can convince me otherwise, a low to mid range machine is all they get. I buy them XBox or Playstation consoles to game on so I will never spend the money on a computer just to game at high fps with top level resolution.
I buy them the tool that gets the job done and a $1000-1200 machine is not it. Those are bought for my wife, me and graduates. One of my younger children uses a laptop running Linux and the other has a 3 year old Acer with Windows 7 (happened to have an ATi video card included for low price). Kids are rough on things and I've had one stepped on (right on keyboard, netbook dead), dropped, spilled on.
Have you considered a Chromebook or does he require more than the software you can run on one? If he's mainly online and doesn't need installed apps, they're inexpensive, come with huge Google Drive space free for 2 years (100GB) and they're fairly quick. Not speed racers, not top of the line in any way shape or form, but functional and throw-away priced ($200-300) if they meet the needs. For most they do not, but you never know. I may get one for my youngest as a Christmas gift and I use one myself as my main daily driver.