When I was in DC New Year's was more of a gala/party night vs big public celebration (maybe because of how large the 4th of July is). In addition to Alexandria, Annapolis also has a good first night celebration. Baltimore also has a decent celebration around the harbor.
My wild card suggestion for you, especially with the kids - the Hershey's Kiss Drop in Hershey, PA:
http://www.hersheynewyears.org
Feeling you on last year in San Diego - we had reserved a special thing at LEGOLAND for their Kids' New Year Eve. Got poured on in the park but still enjoyed fireworks from the hotel.