Which ship will you sail on? My son is gluten-free (he eats adult meals, not kids' meals), and I was disappointed with the Magic's gf offerings for him. He isn't a food fuss, either, and has no other restrictions- he just likes something with flavor, like everyone else.
The Fantasy accommodated him better, but the experience as a whole still wasn't up to WDW standards. Cruise ship dining isn't restaurant dining, as they prepare so much of the food in bulk quantities. That limits their ability to accommodate. His best dining experiences were when he could order an entree on the main menu that happened to be gluten-free for everyone. But that wasn't always an option. The "lighter note" offerings are extremely bland btw- I don't know if they put any kind of seasoning on them at all. The majority of DCL desserts will also be off-limits to gf diners.
I've read a lot of trip reports, & have seen more positive comments for the Dream class ships in regards to gf dining than for the classic ships. Maybe their kitchens are different- I don't know. We're sailing on the Wonder in June to see Alaska, so I'm curious to see what his experience will be there.
A gf diner won't go hungry on any of the ships. Just don't expect the level of accommodation you'll get at WDW. Yes, there are some gf options, but not as many as at WDW restaurants.