Falls Church City has several half-day camps this summer. My daughter is doing an "Intro to Drones" camp that's 9am-1pm and a "Floor Hockey" camp that's 9am-noon. I remember seeing some other options as well, including tennis, pickleball, and coding. I don't believe there's a way to filter for half-day camps on their website, but their catalog is pretty short (at least compared to Fairfax County) so it's not too difficult to look through.