It's rainy, so take them to one of those indoor trampoline places and let them burn off some energy for an hour. Impossible to be sad when you're jumping!

Take a walk in the rain and look for worms. Don't take an umbrella -- he'll love it.

Baseball game.
Baltimore aquarium or Baltimore science museum, then dinner.
Trip to bookstore and they can each spend $x, then go for froyo.
Boat ride along river, then froyo. Or take water taxi to Alexandria (if you're in DC or MD) and have lunch.
Trip to Tysons mall: Lego store, amazing candy store, movie, lunch at that sushi place in the walkway area that has the revolving belt of food.

^^^^ Are you a parent? No parent of 7-YO boys would willingly take them to a mall. And, the dino exhibit has been closed for months.

Go to the Zoo!
Go to the movies!
GO to the park! Take him to try new food, sushi at the Mall?

My boy loved dinosaurs at that age, National Museum? or Play date with a friend is always nice

Go to the mall and see some beautiful artwork in peace.

Air and Space Museum at Hazy Udvar?