Dine and Dance?
There isn't a lot that will suit your needs, but for a good place to dance, you'd probably like Glen Echo: http://www.glenechopark.org/dancing.htm
Old Angler's Inn is quite close. I had a decent meal there, but apparently a new chef has been making some good changes. It's a very romantic spot. Also, further south on MacArthur you'll find some more-casual places, like Kemble Park Tavern, Georgetown Boat House, etc.
I like to both dance and dine, and unfortunately I don't know of a place that's truly excellent for both.
One suggestion would be to look at some dance-oriented web sites that give a pretty good round-up of all of the places to dance in the DC-Baltimore area, and see if any of them match up against your culinary preferences:
The places I know that are good for dancing (Glen Echo, Promenade) tend to have little or no food, or like Cancun Cantina and Nick's have a full kitchen but are only average in quality. Some of the Latin (salsa) clubs in the last link might fit the bill. I haven't been to Liberatore's.
Since I'm willing to travel, I usually combine a trip to a good dance club with a restaurant I want to try that's nearby. But if your wife is less concerned about the quality of the dancing than I am you might have more choices.