Send a message to Looper, he runs the MCB Minecraft server and has been doing a fantastic job for like 2 years.
I'm fairly sure if you keep it to only your son's friends then you won't have any trouble. As long as they behave then you should be fine, I think there are censor options for profanity that you can set up. I know when I played with close friends we would skype or Xbox live chat to communicate faster.
Man the game is $27?? I think I payed like $6.50 for it 2 years ago in Alpha 1.017.