One bad thing about January is potential ride closures for refurbishing. Now you are only talking a few rides, but it may be something to consider.
My vote is for early December. Low points, low crowds, Christmas stuff and
MVMCP is going.
Very end of September and early October can also be good, F&W fest, and
MNSSHP is happening on some nights. Plus you get a little more pool/waterpark weather.
Here is some crowd info:
http://**************.net/2011/09/19/2013-weeks-to-visit-walt-disney-world-ranked-in-order/
Then again, my 2013 VGF points are going to December of 2013, and my 2014 points are going to F&W