We were on the Magic a couple of weeks ago. Our boys are 11 and 12.
Ocean Quest is for 11 - 13 yr olds. You don't have to register them, but you can get a pager for them if you want, but it is up to the kids to ask a counselor to page you if you want to use a pager to keep up with the kids. No wristbands.
They have free time and scheduled activities. They sometimes go other places on the ship, and they have optional dinner time as well. They have scheduled activities on Castaway Cay as well. We found that the scheduled activities were more of a "free flowing" thing - like if it was time for a movie but most of the kids were playing DDR, they wouldn't shut off DDR to start the movie unless they felt like the kids needed a break / settling down.
The Lab was fo the 8-10's. Club for the 3 - 7's.
Our 11 y.o. pretty much lived in OQ while our 12 y.o. came and went. Our boys are completely different and the fact that both of them enjoyed OQ tells me that DCL has found a good mix for the 11-13 set. One of the CMs told me that they switched the ages to make it fit more like schools so that the 11-13s are really your middle schoolers -- so if your child is 14 and in 8th grade, I think they'd find the activities age-appropriate in OQ.
I think for the longer cruises, OQ works well. The shorter ones on the Wonder, there just isn't as much time onboard for the between-kids to have to have something to do if Aloft doesn't work for them. Just my opinion, though. When we sailed on the Wonder last spring, our same DS who spent all his time in the Lab the previous summer and all his time in OQ last month spent ZERO time in the Lab on the Wonder - just no time to go!