I added several more photos from Corbis of press-related areas thru the years, including some great ones of the Press Corps Offices in the old days.
Also, visitor Sandy sent a link to a WaPo article that allows us to speculate that the first mother-in-law is staying in room 327, the large bedroom on the south side of the third floor (bright yellow on the map).
The Elliptical Saloon 
But would the sitting area be a separate room or the smaller room next door?
Loved the human-interest piece on the Obama family and friends visiting DC for THE event.
Hope to see the President one day hold a press conference again with his back against the central entrance to the East Room. This time we want to catch the two kids chasing their pet dog down the staircase and across the corridor and into the Blue Room, with the elder child suddenly realizing what they are doing and holding her finger to her lips in a “shush” gesture while unknowingly staring into the camera. That just might be the ticket to a second term, regardless of one’s personal political notions.
Dennis, the sitting area is probably the room next door, but could refer to the third floor central hall.