My DD has done the activities now on two trips. The first she had just turned 13 and when she finally got up the courage to go, she wished she had gone earlier. This past December she checked out the schedule first thing!
In December. No reservation. Just show up. Cast members run it. She had Uncle at one activity and the same cast members who do the pool parties and family activities. Lei making, character drawing, beach activities, scavenger hunt, etc. Each time she met a couple of kids she was able to meet up with at other times too.
She's also done the teen massage which she highly recommends