Searching for great traditional, warm Christmas dinner for a New York family
What's your price point? I can't imagine anywhere more beautiful at Christmas than the Willard Hotel. They used to have a formal restaurant called The Willard Room, but it's not on the website right now. Might be worth a call. If not, their Cafe du Parc is right next door, and since it's tied to the hotel, it might be open. Then you can still get wonderful photos by the Willard's spectacular trees.
1789 in Georgetown is lovely, delicious and historic. And a Christmas evening stroll through Georgetown would be really pretty, and full of photo ops with the little ones. http://www.1789restaurant.com/main/index.cfm
If you are willing to leave the city, and if it's open, Gadsby's Tavern isn't necessarily known for their food, but it's definitely historic: http://www.gadsbystavernrestaurant.com/