Even if I had the money, I'm not convinced the price of the Disney cruise is worth the money compared to the inexpensiveness of other mainstream cruise lines.
You can get a balcony or at least an outside view on other ships doing "better" itineraries to nicer places than Nassau when you compare cruise prices.
I've seen, read, and am up to date on rotational dining, the various amenities, etc..., etc...
I wonder if renting DVC points would be better for going on a disney cruise. (I doubt it though, because they always tell DVC members that it's better to just use your points to stay at a resort and pay with money to go on the cruise.)
If you are prone to sea sickness, it's best to choose the right time of year and cruise location.
For example, cruises out of texas and louisiana that go through the gulf get some fairly choppy waters. (And the boat has to go close to a top speed to make it to its destinations). I did an NCL cruise in Feb 2009 from New Orleans to Costa Maya, Cozumel, Belize, and Guatemala. It was really movin and groovin that first and second night. And the sea day was pretty full of motion too.
However, a simple short cruise from Miami of Ft Lauderdale to the bahamas (aka disney cruise) it's a short trip in less choppy waters. Also, it only takes about 2 to 3 (maybe 4) hours by boat to get to the bahamas. So cruise ship are just sort of idling around in very smooth waters that they can find in order to stay out to sea for the night or for the sea day. Because they're not going faster and the water isn't as roungh, sea sickness is not as much of a concern.
If you do get sea sick, dramamine helps. If that doesn't work, try stronger stuff from the ship's doctor.
You're not going to get better by doing or taking nothing until the motion stops or you get used to it after several days (and maybe not even then).
I would also try not to get adventurous (in your diet) or eat funky food the day before disembarkation. That way there are no other factors which might make you feel sick. A simple light meal which make you feel full and good is a good idea. Also, light snacking that keeps your blood sugar stable is good for being at your best when the sea sickness comes. (No soda pop or ice cream or dairy or sugary snacks like doughnuts or candy bars.) Also, the state of whether you feel really full or backed up will affect how you handle sea sickness. Just think of going on a roller coaster or mission space after a giant funnel cake.
Not that it applies to miranda, but no alcohol if you're going to be prone to sea sickness.
But when it comes down to it, have your parents ask a school nurse or any nurse or doctor your might be seeing (at a routine physical or something) what would be okay for sea sickness at your age. Different rules apply for medication based on age and weight at different times. Read labels and follow directions carefully.
But the best is to try and avoid the motion that causes sea sickness by getting the right cruise and cruise ship. (Bigger and newer ships have better stabilizers and less prone to problems.)
Also, get a cabin the middle of the ship (middle from front to back) and on a lower deck for combating sea sickness. Also, an inside cabin in the middle of the hallway is better too. The good news here is that these rooms/cabins are also cheaper.
The stabilizers can dampen the side to side rolling of a ship, but nothing can stop the front to back pitching of the ship or the rising and falling of the ship in heavier seas.