Queue when full
The booking form turns into a waiting list when the last place goes.
In the paid plans
When the last place goes the form does not simply say sold out. It offers to take a name and an email for the queue instead.
A sold-out night keeps collecting the people who wanted to come, which is the list you want the moment somebody cancels.
More in Waiting list
A full night is not a dead end: the queue turns a cancellation back into a sale.