only place i can think of is 'denny's'-and i think thats just one night a week. most places have tossed the kids eat free concept out with the advent of cheap kiddie meals. some of the chain buffetts offer cheaper prices for kids (depending on their age)-but i honestly have'nt seen any place that let the kids eat free since i was a kid.
The Old Spaghetti Factory in Fullerton near Anaheim offers a free kid's meal if your child participates in their reading program. If a child reads five books, they gets a free meal: