Contact Carnival's special needs department email@example.com
they can probably work with you. Many ports have import restrictions that all cruise lines seek to honor. I have never seen anybody stopped trying to take food off the ship.
Many years ago a friend of my organized a Celiac cruise on the Big Red Boat. I hope you are able to have an excellent time.
All I ask is a tall ship and a star to steer her by; John Masefield
Carnival: Glory 2004, Destiny 2008, Splendor 2009, Freedom 2011, Valor 2012, Dream 2013
Celebrity: Summit 2011
Princess: Ruby 2010, 2014, Caribbean 2013, Coral 2014, Regal 2014, 2016
Star Clippers: Royal Clipper 2015