These questions come up a lot in the Christmas Superthread! I've almost got the answers memorized!
We still don't know if the CM parties will be held on 12/5 and 12/6 or on 12/12 and 12/13. All I can say is that last year, the CM parties were held one week later than they have normally, traditionally, been held - and we had no idea why that was the case, so we don't know if it will be that way again this year! Will the CM parties revert to their usual early December dates, or will they repeat last year's scenario and happen the following week? We just don't know yet. I don't think we learned the CM party dates in 2010 until November! (I hope we don't have to wait that long this time!)
As rentayenta said, it's hard to tell if there really is a true slow season anymore, and especially during the holidays. The holiday season is extremely popular, increasingly so each year, so unless it's raining over that specific week then I'm not sure if it would be super slow. But it might be substantially slow
ER compared to other holiday weeks, and that's a good sign.
The week after Thanksgiving (which is when I am going to be at DLR this year) is said by many people to be one of the least crowded weeks of the holiday season (not of the year, just of the season), while still getting the full array of holiday offerings, including Santa & carolers at the hotels, etc. People say it's delightful. It's a good time slot, right in between Thanksgiving and Christmas, when people are back at work and school. So I would imagine that if you were to go during that week and then go again in the week right before Christmas, you could see a huge difference in crowds.