Thanks guys
After some thought, we ended up buying the game for him on the weekend. He was due a reward for some very good behaviour, and this is what he really wanted.
So far, my son seems to be enjoying it and he has remarked several times how much friendlier, better-mannered and more intelligent players seem to be, compared to "Runescape." The latter game is really nasty and "grouping," there seems to mean ganging up on other players in the Wilderness and robbing them of their equipment. (you can't choose whether or not you play PVP)
Because of his experiences there, we weren't overly worried about WoW. As far as profanity and such goes, he knows what it is, and he just tends to ignore the idiots that use it excessively. For 10, he's actually quite smart and mature.
My one concern was how his trouble spelling would affect his interactions (he's a bit dyslexic), but even that does not appear to be an issue.
The only thing we have noticed, is that he is going to need a new graphics card. Right now he is getting quite a lot of flashing, and some freezing.
But again, cheers, I really appreciate the input.