We went the 8th-12th period last December and that wasn't overly busy. It wasn't the emptiest I've seen it though. The longest ride queues I saw was probably about 30 minutes, however that was for the popular rides, such as peter pan and it was during the afternoon. Mornings and things were fine. I'd say the week before is a little less busy from personal experience (a few years ago we went during the first week of December and it was less busier). But as DLPdaft said, any of those dates will be fine really, nothing terrible in terms of business

In case you wasn't going to already, I'd definitely recommend making use of the magic hours if you do go. The park was practically empty during this time and that really helped us explore + get things done quicker