Thanks to Diana for recommending Merriman’s Fish House:
I have a restaurant to recommend that I went to while in Kauai. It is called Merriman’s Fish House. They have locations on multiple islands, but I went to the one in Kauai and they were great at accommodating allergies. They have gluten free labeled right on there menu, but I called ahead to mention I was dairy free and garlic free as well and they handled everything wonderfully! The waiter worked with me to be able to have something safe for me to eat and that I would enjoy. We loved it so much we even came back!
Merriman’s Fish House specializes in fresh cuisine with local fish, beef, and produce. They have two additional and similar locations on Maui and the Big Island. As an added bonus for more casual evenings out, they have a location on Kauai, right next door to their fish house, that serves gourmet pizza and burgers. All Merriman’s restaurants appear to be quite accommodating, with gluten-free recommendations right on the menus (they even have a gluten-free pizza crust) and fresh specialty dishes, such as their 100% Kauai Vegan Pizza.
See the website below for addresses and phone numbers.