Do yourself a favor, and don't buy a Surface RT. I work in IT and got one the day they came out to evaluate if they would work in our business. Long story short, they don't. The only apps you can install are from the Windows Store. And last time I checked, they only had maybe 1,500 apps. The app selection isn't nearly as good as what is available on either iPad or Android. Admittedly they are a new platform, but kids will want the apps that can interface with their friends and the popular social networks.
They do have some cool features, but are really limited. Some things that should be really simple and easy to setup, like email, isn't very straightforward. Things like switching between portrait and landscape is really buggy, my battery life is terrible, a fraction of what my iPad provides. For everyone who says that an iPad is really just a big iPhone, the Surface RT is really just a big Windows 8 phone. Which no one really seems to like. If you have a huge investment in the Microsoft stack, so already have a MS account, XBox Live account, use exclusively MS products for software, then you may love it. But if you use anything else, you will find it fairly irritating to use.
The Surface Pro (expected to be released in Jan) can natively run any Windows application, and shows much more promise, although the price will be much higher.
If he is really insisting on getting one for the holidays, don't but it until he gets his hands on one to try it.