My wife is celiac and she has found that cruising is the easiest way for her to travel.
We always email special services to let them know. We also note it when we book and it shows up on our invoice under her name.
Talk to the maitre d at the MDR, and also make sure.your waiters know. They take your order the day before for the next night.
Nothing to stress about, you won't be the only one and they really go above and beyond to make it enjoyable