Hi Ryan!
Thank you for visiting the Moms Panel!
With regard to crowds and weather, there is not much difference between the week before, and the week after Thanksgiving week. The crowds will rise during Thanksgiving week, and will be high on Thanksgiving Day.
The Christmas decorations will be completed by Thanksgiving week, so if you want to be guaranteed to see them all, the week after Thanksgiving would be your best choice.
Mickey's Very Merry Christmas Party at Magic Kingdom park begins on November 9-December 21, on select nights.
The Candlelight Processional at Epcot starts on November 23-December 30. If you wish to take part in either of these, the available dates might help you make your decision.
If you have any other questions, please come back and ask me - I would be happy to help you plan your magical vacation!