@Arnon0, I can understand that this would be an unpleasant experience for you. How wonderful that you live in a situation where people are making an effort to keep all areas clean.
It appears that your guest has acknowledged that you provided very nice accommodation as per your listing. They have a booking with you, arrived safely and were greeted well by yourself.
If they choose to walk away, then they may decide not to cancel via AirBnb, and instead to allow you to receive your fee without any challenge just as if they had stayed. It is not necessary for you to cancel the booking, that is their responsibility.
If they choose to cancel then your cancelation policy comes into action via Airbnb automated systems, and you do not have to do anything to claim or distribute money It is all automatic and your funds are still due to you.
Keep in mind if they do not actually "cancel", the room is still "theirs" you cannot re-book it across their dates, and technically they are still also responsible for the property. So keep it all nice and secure until it's time to greet your next guests.
The money that you are paid is in large part for making the room ready and retaining availability for them. It appears that you have honoured your aggreement.
All the very best to you. Enjoy the beauty of your neighbourhood, because it sounds fine.
Regards, Christine.