Hello!
$2500 is definately doable for Disney.
I would make a reservation for the timeframe you are looking for, and put the minimum down on the room (mostly 1 night to hold room, if that). Keep checking the discounts for the room.
About one week from when you plan to go, you can check Priceline and try to do Airfare and Hotel.
My parents and two teenage siblings went to Disney last summer, spur of the moment in August. Four nights, five days, rental car and airfare from Phila for less than $1000. They still had to pay for tickets to getin parks, but if you can get a cheap price through Priceline, it may be worthwhile to fly. We always drive from PA, but the drive does get old! It seems to take forever to get there.
If you plan to drive, don't forget you will need money for gas and two additional nights stay (one night for way down and one for night back)