From another teens point of view.
I have been on three
DCL cruises, all a week long. Each time I haven't really had many rules set, which I feel allowed me to enjoy the cruise a lot more. I am not one that likes to stop doing something because its 5:30 and I need to go change for dinner, or its 1am and I am a curfew so I have to leave the Stack or leave the group of people I am hanging out with, since that is really when you get to know a .lot of the people
My mom has taken post its and pens so we can leave notes in the room for each other, on my most recent cruise this was utterly pointless since I was only in the room to change clothes for the most part, spent maybe 30minutes in there one night eating dinner while watching a basketball game or something. This seemed to work the best though. We would also see each other around the ship a few times a day and touch base on what we were doing for the rest of the day and what we would do the next day if it was a port day.
As for getting to bed early on customs day (for Eastern cruises) and the last night, a curfew might be good those days. On my Last cruise some of us were always up really late. Something like 3am was the earlier I ever came for the most part, there was one night I went in at 2:20 and another I was in at 1::30 or so b/c the next day we had customs in St. Thomas. We were also up till 4:30 on the last night, and had to be up at 7:30 to get ready to get off the ship that morning. Wishing now that I didnt do that.
The older teens (15-17s) dont like hanging out with the younger ones(13-14s) much. On all my cruises they have had a tendency to be really annoying and be in the way at times. I have meet a few older 14 yr olds that were very mature and did hang out with them quite a lot but you couldnt tell they were 14, they seemed much older. Last week (March 15th-22nd) there was 130 teens in the Stack for the 411, and it seemed about half were under the age of 15.
Also keep in mind that they will be no long allowing 13-14s in the Stack as of May 10th. This is what Taylor in the Stack told me last week, and it has been rumored for quite a while.
And as for finding their way around the ship, it will be no problem. It takes me about a day to get my bearings back when I go back onto the ship. My first cruise, I was all over the place and figured it all out pretty easily, I would say by the 2nd or 3rd day.