Group Vacation

[GoneFishing]

My extended family and I (15 people) are planning to take a trip to Disney World from December 23rd until January 1st. Do you folks know if Disney gives any discounts for tickets or rooms for 15 people (5-6 rooms)? We would definitely rather stay on-site if at all possible. Any tips for large groups visiting Disney during the Christmas week? Also, do airlines give discount/group rates? We are in the beginning stages of planning all of this out and any help would be greatly appreciated!

Thanks!!
David