First I will tell you that I'm sure it depends on the CM, but in my experience they are strict. We wanted to go this year and my son turned 16 the day we were coming home. They wouldn't let us go. No problem because we go often and we'll just do it next time. I didn't push, maybe if I had they would have let us. Now I know you will get a ton of replies that tell you that their child was 14 or 15 and they went and this is why I am sometimes hesitant to post, but I can only tell you what happened to us. Take is with a grain of salt. I will say this though, if you have any thoughts of renting water mice they are very strict with this. You have to be 16 with a valid driver's license. We did try to convince the CM at the Poly to let our son drive as he would be 16 in 2 weeks, but she would not budge.
Good Luck and have a Wonderful Trip!