The Bushes wouldn't let the Obamas stay at the Blair House, the official temporary residence of the incoming president-elect's family, because, who knows, they have people in trying to fumigate out the stench of eight years worth of Laura's pack-a-day habit or something.
So until January 15, which is only a couple days before the inauguration, the Obamas will be staying at the historic and luxurious Hay-Adams Hotel, which is right across the park from the White House, and also it is haunted. Here is the hotel FAQ.
They had to move to DC early so that their little girls would meet the residency requirements of the fancy elitist private school they will be attending.
Beltway Insider Tip: The proper way to pronounce the name of the Hay-Adams is in a funny Lou Costello voice.