Good place for wedding rehearsal?
the food sucks (well ok, just boring and not memorable, it's like a stylish Chevy's) but Lauriol Plaza tents and heats their roof terrace in cool weather.
there used to be an Italian place (long gone) almost next door to Bistro du Coin that had a 2nd floor/mezzanine space that was nice. I wonder what went in there.
Not sure what kind of food you are looking for or what "moderately priced" means to you. Lots of places have private dining rooms for parties your size. I would have suggested the private room at Grapeseed in Bethesda if you hadn't said in DC; I would still suggest it if you are flexible. It's a wine bar & restaurant with an awesome private room that is in a little wine cellar type of thing. Right in Dupont, maybe Urbana in the Palomar Hotel. Their food is good, med/American and it's pretty large; not sure if they have a private room though. There are oodles of ethnic places in that area that may have a private room and would be reasonable. Any of the nicer hotels in the city would be used to hosting this type of thing I'm sure.