OP, I feel your pain. Last Jan we took my best friend and her husband. He's the Plain Jane eater and she's the adventurous one. Never did I stress more about food than that trip.
The great thing about Disney is that you can get most things "dumbed down", without sauces or weird sides. So that is what we did. We ate at Ca Grill, Jiko, Boma, 50's, Sci Fi, Beaches and Cream, Le Cellier, Coral Reef, Yak n Yeti, Columbia Harbor House, Yachtsman Steakhouse.
The only two the husband really did not like were Boma (even the plain food had weird spices according to him) and Coral Reef was a little tough too but he managed with a Ceasar salad there. I tried to rotate the the plainer places with the adventurous places so that he was getting at least one meal per day that he was happy with. He just asked the wait staff to leave off sauces, weird herbs, tomatoes, etc.
Good luck.