This likely won't answer your question, but is somewhat related to your 'decent room' question: I was at the Marriott yesterday. I had gone to see if my reservation which was made in October of last year could be confirmed for a double room (a room with two double beds instead of a single king-sized bed).
The lovely young lady at the customer service let me know that there were no double rooms available DC weekend. They offered a roll-up cot for our king room.
I have stayed at the Marriott Marquis in ATL for non-DC events and the rooms are very nice but not palatial. We are just going to bring an air mattress and make due with the space we have. Kids will love getting a chance to sleep in a closet.