I am celiac and cruise a couple weeks each year.
I bring a lot of prepackaged snacks with me for my travel days to and from the ship (2 flights each way), to eat on the ship, and at ports.
You're not supposed to bring ship food off the ship. They have dogs sniffing everyone's bags at some ports looking for food, but prepackaged food is ok.
I bring an unopened jar of cashew butter in my checked luggage. I bring several bags of tiny milk chocolate chips (from the baking aisle), Rice Krispie treats, protein bars, etc. in my carryon luggage.
The Windjammer has yogurt in big bowls that people scoop out of. I ask the worker for individual yogurts (they keep them in a fridge behind the counter.) I put them in our cabin fridge to eat later as snacks with my cashew butter and chocolate chips.
I eat lunch every day at El Loco Fresh. The first day of each cruise I talk to the head person there to make sure I know what is gluten free. I don't take anything from their condiment bar because of the possibility of cross contamination.
I always get early dining and preorder my food for the next day.
i trust the desserts at the Cafe Promenade because they are behind glass and you have to request them.
I'm very careful in the Windjammer buffet.
Have fun!