Another thing to keep in mind is that there's basically squat to eat around the BWI area outside of the hotels themselves. McD's, Wendy's, a bad convenience store (well, bad for groceries, I've never tried the deli in there), that's about it. It really surprises me given the number of limited service hotels out there. Expect to eat somewhere else entirely, or in the hotel if you choose something with full service. Given that, something in walking distance to Arundel Mills doesn't sound like a bad idea.

Note that the shuttle to the *rail* station generally refers to the BWI Rail Station where the Amtrak and MARC trains stop. This isn't the same as the light rail which can take you into the Inner Harbor and such. You probably won't be making use of the heavy rail station unless you actually go to DC. That said, I gather if they're going to keep someone on call to go to the Amtrak station they can take you to the light rail instead.

6-12 people pretty much rules out some of the ways of getting hotel rooms I mentioned, as I'm sure you're aware. Just be aware of what you're getting into at BWI: no services within walking distance or even really within driving distance (I've driven all around there; any services beyond the gas or fast food and that movie theatre down there are a ways away unless something new has come up). So choose your hotel accordingly. The standard issue HI there really is adequate and does have a restaurant/room service (though I don't think it's 24 hour room service). I've never stayed at the Four Points, and I can't think of any other IC/SPG properties there. Lots of Marriott and Hilton.