Hi, if meeting guests and there is more than have booked, open up the ipad/ tablet/ laptop/computer and go to your reservations, request an alteration on the relevant booking, adjust the numbers. The tariff will adjust up, accordingly. Then get your guests to open up their own airbnb site and accept the alteration you sent through. Of course you can request them to go online and send the request in the same way. Cancellations are not the only option.
Do this before granting access. If the guests don't accept the alteration, they don't get access. This can only occur if you have sufficient facilities of course, if not then the booking cannot proceed, you can assist/ supervise while your guests book an extra venue for the extra numbers. If you don't live onsite, you are more vulnerable to these events. By ensuring that you make it clear you will be present at the site for check in and during the guest stay, you will discourage this type of event. Hope this helps. Best regards. Christine.