My kids had self check-out privileges in Dec/Jan (8 and 11), which was fine with us b/c they had to stay together and both had devices to text. Next summer, my oldest will have just turned 13, and we'll be sailing with their cousins, one of whom will be too young for self check-out. The other cousin and my son (obv, ha!) will both be old enough for self check-out, so I figured an adult would always have to deal with checking the younger one in/out. If we can give my daughter the ability to do that, it will be pretty useful and she would LOVE the responsibility. They aren't in our cabin, but our reservations are linked. I never read the fine print, b/c it had no bearing on our last sailing... I just assumed it had to be an adult!