Ugh, welcome to late summer in the DC area. It is just too hot to go outside. No matter how wonderful the playground, my daughter is melting after 15 minutes. Time to check out some indoor options.
I was pleasantly surprised to discover that DC had an aquarium. Though small, it is the perfect hot day activity. It is located at the Department of Commerce Building and is a fairly easy metro ride from Arlington. Most of the viewing tanks are high off the ground but the first one you see has turtles and alligators and that is on a toddler level. We spent a lot of time watching the turtles.
No restaurant but a nice store.
COST: $7.00/adult, $3.00/ages 2-10, FREE/under 2 years