My kids love the decor at Firefly - and the terrace provides a good tantrum exit strategy. Poste does a good job of taking care of kids (i.e. bowls of fresh strawberries and quick service.) and again, the hotel lobby = good exit strategy. Although not much of a food destination, it doesn't get more kid-friendly than the American City Diner in Chevy Chase. They have a juke-box and a train that travels through the dining room. Maybe just for breakfast . . .