If you've got kids, here's a good indoor option. The other day I was walking around DCUSA and saw a sign for "Magic Ground: now open."
Located on the top level, it's an indoor playground, game room, art space, and more for kids. There are ball pits, climbing areas, slides, trampolines, toy cars and trucks, swings, and such. There are also Nerf-type air guns, which to me sounds awesome.
It doesn't get great Yelp reviews, but I remember always enjoying these kinds of things when I was a kid, and my friend who has a three year old says he's been 6 or 7 times and she loves it. (He recommended bringing a friend, otherwise it's kind of boring just watching kids run around.) Others on Yelp said it reminds them of Discovery Zone, Port Discovery and similar things but can be a little chaotic.
It's $10 for an hour or $15 all day if the parent or guardian sticks around, and there's also a $20-two hour drop off -- although Yelpers say there aren't many staff so maybe dropping off isn't the best idea. There's also apparently a restaurant and coffee shop but reviewers report it not being open. They also host birthdays and other parties.
Magic Ground is on the third floor of DCUSA. Here's their website.