I've been to a few.
In Crystal City, there is Ted Turner's Montana Grill. Not too pricey, okay food, kids will probably enjoy the big bison on the wall.
There is a Jaleo there which is tapas but haven't eat at that location so I don't know the setup for large groups.
There is a McCormick & Schmidt Seafood restaurant there. Also Legal Seafoods but it is small and not conducive to large groups.
Over at Pentagon Row, Labanese Taverna has a neat atmosphere and I have noticed some large tables in there.
I believe Rosslyn has a Melting Pot restaurant.