Hi, im not going on this cruise but go to the teen section of this site and post it on the message board there. Then teens going on this cruise can reply and your son can possibly e-mail them before the cruise and get to know them.
Even if he doesnt meet anyone on here, he will meet someone on the ship. I'm a 15 yearold guy and just got back from the Carnival Pride, which is just like the legend. Just tell him to not be shy and go up to someone the first night and ask them a question or something. The're just as interested as meeting someone as he is. Thats what I did, and i had someone to hang out with whenever i wanted. Just tell him to not be shy.