I know about teens being grounded from the computer. Mine gets very limited computer time and I have parental controls galore!
I don't know if you guys drink, but my DH like a beer or 2 on the weekend, since everyday is like a weekend day on the ship he goes through some beer.
DCL does not have a problem with you bringing it on board yourself. We even throw a few in the towel bag when we head up to the pools. This is a huge saving for us. I'm not much of a drinker but I may bring my Magic Bullet since it is so small for a pina colida or two. I also lug on a ton of bottled waters.
The first time we went to St. Thomas we just did the cab to Megan's Bay. It was incredible! For lunch we ordered room service sandwiches and I had packed baggies to but them in so we could take them. At the time it wasn't a cost saving thing, just didn't know what they would have at the beach and didn;t want to have to come back because kids were hungry.
St. Maarten we did the Eagle Catamaran and loved it! But sometimes you can find excursions that aren't through DCL that are cheaper.
We've never done excursions on CC, not for trying, twice we've had parasailing cancelled on us due to weather. But it's never been a big deal. Castaway is awesome, if you get tired of the beach there are all the free games a Groupers Pavillion or playing a good game of sand volleyball.
I pretty much tell my kids if they want smoothies and game cards for videos they have to spend their own money. My son plays enough PS2 at home I hate the idea of spending times in a dark room playing more video games when you are on this incredibly beautiful ship.
Start now with 4 envelopes and label Head Waiter, Server, Room Steward and i forget the 4th one. If you stick some $$ each week hopefully by the time you go you have them all filled with the basic amount. And it is one less thing you don't have to charge on the ship!