One more thing on restaurants... You haven't mentioned the ages of your kids, but if they're older tween/teen, you might want to go to either Adams Morgan or the U Street Corridor, walk around a bit and choose one of the funky restaurants, maybe even one with outdoor seating. Your kids will love it. Your wallet will love it. (Remember, it's still DC, where thanks to our government dollars generously providing outlandish salaries, everything is relatively expensive.)
I wouldn't go to either of those areas with younger children, but older kids will think it's cool. Not that there is a safety issue or anything wrong with younger kids at either location, it's just that the experience will be lost on them and you'll spend more time keeping track of the kids than enjoying it.