Hi - I am celiac and our next cruise (NZ and Australia) will be our 4th (2 Celebrity, 4 HA). I have had great experiences on all of our trips with the staff onboard meeting my gluten free requirements. Eating off the ship is another story, so I generally avoid the hassle. However, when we have been on excursions in non-English speaking countries, especially where a meal or 'snack' is included, it can be tricky.
You should check out this website: https://glutenfreeglobetrotter.com/resources/glutenfreetranslations/
You will find travel cards in any language that explain what celiac disease is and what foods can/can not be eaten. They are great to print off or have on your phone to show at restaurants etc. I used them several times and it really helped communicate my needs!
Jill