Hi;
In regard to the room block, if you had it so that the guests were responsible for paying for the room (versus you being responsible and paying for guests), then you should be in the clear. What usually happens is that the rooms that weren't booked in the block at the rate you were given now become available for others to rent. If you'd like to extend the time folks have, you might want to talk with the hotel rep that is handling your account and event.
Best wishes!!