As lanejudy said, if you want the package extras such as DQ admission you have to book a package, but adding tickets to a room only reservation doesn't make it a package. You would have to cancel the room only res and book a package with full payment at time of booking.
One possible problem - the deadline for cancelling a room only res without a penalty is 5 days in advance of arrival. The penalty is forfeiture of your deposit. I don't know if the penalty is waived if you book a package at the same time. Something to look into if you decide to do a last minute package.