If you go to carnival's web site all the rules for bring stuff on the
ships are there.
No you are not aloud to bring your own on the ship except for one
bottle of wine per person.
you can buy stuff on the islands and they will take it from you getting
back on the ship and return it to you on the last night of the cruise.
there are limits you can buy to bring back to the states so be sure
the check that.
Drink prices on the ships are not bad at all.
you can try to take stuff on your first day and if you are lucky you
will get it on the ship. if not say good bye to it for they will not give
you that back at the end of the cruise.
Just cruise and have a good time...