Wow, thanks everyone, that's really encouraging.
We are sailing HAL this time, and we have let them know in advance, but I just didn't understand HOW I'd find the gluten-free stuff. My big worry was trying to resist those wonderful bread rolls at dinner in the dining room, but if they bring me gluten-free ones, - hooray!
I have learned to live without sandwiches, and I love rice pasta, so I am doing OK at home.
It's resisting all the good stuff that I know will be on a cruise that's going to be hard. MY problem, MY will power, I'm not worried about going hungry!