Above hotel and attraction suggestions look great. Makes it hard to add something super insightful with my 2 cents. Haven't been to the spy museum but have heard it is a bit juvenile, more meant to appeal to kids.

Not sure if a 13 year old is more sophisticated than the target audience. . .

Definitely peruse the Smithsonian website- can check out all their museums to help gauge if they'll be of interest to your brother.