We no longer take our kids out of school for vacation, they are too old now and the workload is too huge, but in 1999 we went to WDW the first week of December. It was great, cool, and not too crowded. I would think Thanksgiving would be pretty crowded, but anytime that the majority of kids are in school it should not be that bad. Most schools have a few days prior to Christmas until a few days after New Years off, these times would definitely be the most crowded. Hope this helps.