Another question: crabs for lunch
Maryland has had a moratorium on crabbing that started November 1, so it is unlikely that you will be able to get local crabs. In any case, I'd concur on Gunnings as well, and you're right to notice that two different addresses have been posted. Both have good reputation for crabs (I think they are related).
If you'd like to go into Baltimore, you can go to Bo Brooks in Canton--although stick to their crabs (when they moved into their new place, they expanded the menu to include "upscale dishes"; I'd stay away from these things).
You might try Gunnings in Brooklyn, just south of Baltimore for crabs. Call them to make sure that they are open.
Gunning's Crab House
3901 S. Hanover St.
Hours: 12 p.m. - 10 p.m.
Call for directions.
Unfortunately it is highly unlikely that you will be able to find local crabs at this season.....
If you have the time, I'd like to suggest that you go to Cantlers (near Annapolis) for your crabs. It is considered the best place for crabs and atmosphere, too. Plus, it's a straight shot from there to BWI up Rt. 97.
If you can't do that, I'd recommend trying the Bethesda Crab House in Bethesda. Good crabs (difficult parking) and sort of on your way to the airport if you are going around the beltway.
One suggestion is to call where ever you choose earlier in the day to make sure they have crabs since it's the off season.
You might want to try The Cracked Claw at Peter Pan in Urbana, which is probably about halfway between your house and BWI. I don't know the Sunday hours but the phone number is 301-831-1200. This place is a seafood place which also has Off track betting if you like that sort of thing. It's casual, paper on the tables etc...It's just South of Frederick off route 355.