Actually, it will not be problem because when they do divide up, the age groups are 13 & 14 and the other is 15-17. So you will be 15 at the time of the cruise.
In looking at the teen navigator from 6-2004, here are some basics:
Day 1 & 2 there are no division of groups
Day 3-13 &14 have the hidden mickey challenge while the 15-17 activity is "go Fetch" (???) This is for about 1 hour
Day 4-15-17 play Bingo while the 13-14 Play Glow BB. Obviously evening! 1 .hour
13-14 invade the Lab while the 15-17 have an Exclusive activity (?)
1 1/2 hrs.
Day 5 13-14 have Bingo nothing special for the 15-17 1 hour
Day 6 13-14 ps2 tournament while the 15-17 have 2 on 2 hoops 1 hour
13-4 2 on 2 hoops while 15-17 Mix and Match activity 1 hour
Day 7 there are no division of groups
Now keep in mind that navigators change, but hopefully this gives you a good idea. It really is only a total 6-7 hours during a 7 night.
Hope this helps!!!