Hey I'm goin on the Constellation April 12th, the week before you. I've been on Celebrity 5 times before. To answer your questions: Everyone gets an id card thing when they board which is their room key and charge card which you would charge drinks to. This card doesnt have your age or anything on it, just your name and the date of the cruise but everyone who is under 18 is issued a blue card and everyone over 18 gets a white on. So when you go to order drinks thats how they know if you are underage. However, for some reason the past 2 times i've been on a celebrity cruise my name wasnt registered like as a minor or soemthing so i got a white card. So maybe you'll get lucky... If your parents dont care that you could drink you could switch them cards so you could charge drinks to it. They don't like check your age or anything when you use it.
The crew also sometimes doesnt care if your underage or not they will sell you drinks. This happened to a girl i met on my last cruise, she got drinks every night from this one bar. But to answer you question... sometimes they dont care at all. Just like to get into the disco at night you are suppose to be over 18, but a lot of times the dont care... or they don't even realize how old you are. If you hang out with an older crowd like 17-20 chances are they wont notice.
At night, some people went to the disco and on the Millennium they had this like *dance under the stars* thing on the back of the ship on the deck for teens. Some of the activtis are kind of cheesy that they plan for teens. But the first night the have like an introduction night where you go and meet all the other teens and they tell you about their teen program. A lot of time what happens is the first night teens go and meet people and then they hang out in a group for the rest of the cruise. Also, since its spring break there will definitely be a lot of people your age on board..
but anyways...this is getting really long so i'll stop typing...but if you have any questions email me at DreGurl15@aol.com
Have fun on your cruise! ~Andrea