Well if you go to Carnival's website on the first page look at Plan & Book, when you get the drop down look to your right and you will see FAQ's and Embarkcation Documentatin. Lots of all the imformation you need. Passports are not needed if you are on a closed loop, meaning leaving and returning to the same Caribbean Port. However if you need to fly home for an emergency or any reason you can't without a passport. I would think you could certainly book now and if the prices go down they would honor them if you have not made finally payment. Have fun planning !!