I just returned from the CP and posted my review. You will have a great time! In terms of suggestions, I will focus on cruising with teens---we didn't do it this time, but have in the past:
Bring (or buy on board) one of those thingees that go around your neck for your cruise card---have the purser's desk punch a hole in it when you all get onboard. That way it is less likely to be left behind, and you don't have to worry if you are going to the pool and don't have a pocket to put your card in.
If your kids drink soda, the "coke card" is a good deal...a flat rate paid up front gets you a sticker for their cruise cards that will entitle them to all the soft drinks they can drink, including dinner. Soda costs from a bar can really add up, otherwise.
If you have the chance, and the inclination, feel free to carry a six pack or two of bottled water onboard. It is allowed by the cruiseline, and it is expensive to buy onboard. You will see the cruise line selling chilled bottled water everywhere you look now, not just when you are getting off the ship in board. I was really surprised how much they were pushing the sales of bottled water in the Horizon Court and Cafe Caribe.
Be prepared to give your teens more slack than you might at home. Depending on your teens, they may meet you for dinners, but most parents traveling with teens on cruise ships do not eat 3 meals a day with them....we really enjoyed going into port with our daughter and her friend, and dinner each night was a must, but during sea days they pretty much got up when they wanted, and found their own place by the pool or wherever they wanted to be during the day. Don't expect the 14 year old to want to hang out at the teen club. In our experience, most teens go the first night or maybe two, and then just meet up with the other teens they have met, rather than regularly attending the organized activities---although on our recent cruise we did see two young teenage girls actually doing a scavenger hunt on the second sea day.
Our one very firm rule: we did not allow them to go into anyone else's room....or bring anyone to their room (the teens had their own room, which I highly recommend if they are responsible, and if your finances allow it).
If you go to St. Maarten with them, do the America's Cup. They will have a blast.
Make them pose for pictures at least one of the nights, even if they balk. They (and you) will be glad you have them to look back at.
Make them use the safe in the room for their vaulables on sea days....cash can't be used onboard, except for tipping for room service, and their is no reason to carry a wallet with them on sea days.
Remind them if they order from room service to tip. This does not occur to many teens, who think it is included.
Hope these suggestions are helpful.