The Everyone at Kids' Price promotion has been run Jan-April the past couple years. This Spring, they are offering the 5 days for the price of 3 day parkhoppers.
As for promotions in December, the only one currently being offered is the 4th night free if you stay at one of the DLR hotels or good neighbor hotels.
If you are willing to skip EE, you could purchase your tickets through the gaydaysanaheim website and get a really good bargain. Those tickets don't expire until December 13.