Maybe ask if you could postpone the stay to a different weekend? I have no idea if it will work but the hotel might be inclined so they keep the revenue, make a customer happy and also get to rent out the room at a higher rate.

Also, if they won't work with you you may want to check Marriott's policy of getting points (and night credit) in a no-show situation. I know another chain (SPG) will give you the points but no stay or night credit.