And it worked out great!
The following is a cut/paste from my response to someone else asking about this in the past:
I think this little taste of independence was really the highlight of Amanda's trip. We are relatively cautious parents and don't often allow her this kind of freedom. Yes, we were very comfortable giving her this freedom on the ship and it worked out fabulously for all concerned. She has moved up another notch in showing us her maturity and responsibility.
The way it worked is that we got one pager for our two children. DS6 and DD10. When DS6 wanted out of the club, they would page us and we would go and get him. Pretty simple. We worked out our own rules with Amanda. They were as follows:
1)She could sign out with a friend only...never by herself.
2)She must have a destination in mind...no signing out to wander the ship
3)She would have the lab page us with her destination.."Amanda signed out to go to the movies with friend", "Amanda is back at the lab", etc.
That was it. The lab made it clear to us that it was Amanda's responsibility to have them page us. Once we gave the OK for her to have sign in/out ability, it was not their job to notify us, it was hers. It worked out great! We always knew where she was.