I just asked a reservation CM and she said that I could do the dining later as an add-on.
Also, if you book room only, you have 'til 5 days before your arrival to make any changes. With a package, any change made w/in 45 days of your trip has change fees.
Free dining is not being offered as yet for 2006. I always book room only because anything could happen or we could decide to upgrade at the last minute and I don't want to have added fees.