Hi there, Jason. I hope that you got the answer that you are looking for with regards to booking by now. If not, I can tell you that you can definitely book at package for January 2008 now. If you are looking to do a grand gathering, let them know right away at CRO and they will transfer your call to a CM that deals specifically with those.
I have never been part of a grand gathering before so you'll have to ask others for info about that. Same with going in January. I've never been to WDW then. It does seem like a great time to go though as far as crowds and prices go.
You might want to ask any questions about these things on the Theme Parks Boards. There seem to be a lot more people who visit them who would be able to help you out. Best of luck planning your WDW vacation!