Citronelle is definitely your best choice for Georgetown. Also consider CityZen. And although not romantic via atmosphere, the tasting menu at Komi will blow you away.

The best source of information for DC restaurants (I couldn't live without this resource) is DonRockwell.com where there's plenty of information on countless restaurants throughout the area, including servers/barkeeps/managers/chefs/owners of many of them. You could probably get in touch with some of the staffers/owners and see if they could put together something even more special for you.