@Lori271
their cancellation has nothing to do with you and you don't have to do anything. They will be or will not be refunded according to your cancellation policy.
It is between them and Airbnb .
In some cases Airbnb will call you and ask you if you would like to waive your policy and refund more then you should. You can refuse or agree, it is up to you.
Never ever cancel by yourself or you will be penalized.
If you receive a message something like : " Your guest wants to cancell, do you agree? " You should not agree or you will be penalized.
Guest can cancel by themseves, they don't need you to agree .
Here you can read all about cancelation policies (flexible, moderate, strict... etc..)
https://www.airbnb.com/home/updated_cancellation_policies