You should keep checking the December cancellation thread. That's where people would post any dining cancellations for BOG and Chef Mickey's. Good luck
The most likely way you'll get the reservations you want is to keep checking online daily to see if a cancellation comes up. Since cancellations are put back in the system almost immediately it's a matter of luckily being on line at the moment it re-enters the system...the more you check, the better your chances. If you're flexible about the time and day, you will also increase your chances of finding something that would work for you.
For BOG if you don't get a dinner res, you can go for lunch when it is counter service and no reservations are accepted. The entrees are different, but desserts and both soups are identical to the dinner menu. You can also walk around to see all the rooms. The main difference is at dinner there is the photo op with the Beast after you finish eating and wine and beer can be ordered.
I'm in the same boat but for 11/29 to 12/7 and have been looking/waiting for more than a month now. For Chef Mickey, my backup is a dinner reservation we already have at 9:05pm. If I find another time breakfast or dinner at better time, I will definitely give this up.