My youngest is going to be 13 exactly one month after we sail, but after thinking about it and talking it over with him he decided to be in the Lab. He's done it before & loved it and it's his last chance to do it.
Also, other factors:
1) His older brother will be in Common Grounds
2) He still enjoys doing a lot of the things that they do in the Lab
3) He will be the youngest in a club filled with teens ranging all the way up to 18 (his brother turns 18 in the middle of the cruise)
4) He will hopefully have a chance to experience CG on a later cruise
You know your son best & what type of club he will be comfortable in. Our older son is very social & adjusts very, very easily. The younger one, although very friendly, takes longer to warm up to people & tends to try to be "funny"

to 'fit in' & teens don't always accept that.
There are tons of fun things to do in the Lab, as well, so maybe you can check it out & let him decide what appeals to him. I believe that I got the info. from the cruise line website -
www.disneycruise.com.