Question! Can I book rooms at a resort and then go back and book a package or get a discount when they come available?

:
I would like to go ahead and reserve our rooms at the CR for March 2010 but I'm hoping for a discount.

Or should I go ahead and book our entire package(tickets,dining and room) and then can I change if a discount becomes available.

I need some advise from a pro

Thanks!
minnie

DH

DS (9)

DD (5)