My first advice is you should always you a travel agent as they are ready, willing, and able to help answer all your questions and assist in getting all your required items together. They'll spend as much time as you need to insure you have all the information.
Okay, with that said, you'll get alot of good information on this forum from alot of great people.
1) Yes, Carnival will have some special programs for the kids.
2) Yes, there will be alarms and they are quite loud. So if she is super sensitive, I would suggest having her wear some ear phones, perhaps with some nice music she likes to listen to.
3) The only document you should print out is your boarding pass. In order to get that, along with the luggage tags, you need to complete your online check-in. But don't forget your identification. Everyone must have either; a) a valid passport, or b) an original birth certificate and a government issued photo ID such as a driver's license. Minor children traveling with parents just need the birth certificate.
4) Checking in at the pier and boarding the ship is relatively quick and painless, but it depends on when you arrive at the port and when boarding starts. You have to be at the pier 90 minutes prior to sailing, so I suggest getting there 2 hours prior to sailing and you'll usually not have any lines at all.
5) If anyone is prone to motion sickness, you might want to start them on ginger pills a few days before the cruise. They're cheap, easy, and work very well, especially for kids. But it's possible you may feel some motion, so it depends on their ability to handle it. Whatever you take, you need to start it a few days before in order to take affect by cruise time. Waiting until they get sick is too late.
6) The only ID you need to take off the ship is a driver's license and your Sail & Sign card. Kids just need their S&S card.
7) Yes, the A/C & heat is controllable in your stateroom.
8) No, the soda card is not necessary unless the drink alot of soda. Figure about $1.50 plus tip (15%) if you purchase one.
9) Yep, lots to do on a ship. There will be a daily newsletter in your cabin showing all the activities - most of which are free.
10) Lots of good information out there. Start with the Carnival website.
Let us know if you have anymore questions.