We filled out the special needs form ahead of time for GF (both my son and I had been GF for years - my mother had celiac and it seemed likely that my son had it too) and without fail before every meal, the wait staff knew to ask. We ate primarily in the Haven, with le bistro and teppanyaki as our specialty dining. The menus seemed well-labeled and it seemed like it would’ve been pretty easy to get GF food. I’d say that I am more savvy than the non-celiac dx person because my mom had it all my life and we were fully GF at home (she would get really sick so she was very cautious).
However, I had just gotten my testing back saying that celiac was unlikely, and we had decided to put my son back on gluten to get him tested, so we didn’t actually end up GF on the ship.