Family Friendly Eats on Sanibel?
Lazy Flamingo has some really nice fish platters, I'm a huge fan of the tuna, we eat there at least once or twice every trip to Sanibel. Plenty of stuff on the menu for kids too. This would be my first choice.
Island Cow is great with kids, they have a menu that includes pretty much everything.
Mucky Duck works for kids too- pretty loud usually and the menu has kids items. Actually on Captiva, right on the beach, be sure to ask for a window. ;) They'll roll one out for you.