As far as the upscale restaurants in Grand Case, they are perfectly fine with kids, so long as they are well behaved, and I'm sure yours are! I think some of them have kid menus, but I'm sure you could get a simple pasta or similar too. For another option for upscale French food, you could try Dreams, which is in Nettle Bay. They serve breakfast, lunch and dinner, and in addition to classic French favorites, they have kid friendly things like pizza and burgers.