Is there a way to send the invitation to register after a cancelation ONLY to the next person on the waiting list? If not, how do I disable the event cancelation email message?
We do not support that option. So in your case, disable the email is the right option
Go to Events Booking -> Emails & Messages, find the subject of the email and empty it. After that, the email won't be sent (the same rule is applied to every email sent from the system)