@Kathryn162 Based on your cancellation policy they will get a full refund if they cancel more than 5 days prior to the start of their stay.
That said, if you had a strict policy I suspect that they wouldn't have booked given the current issues
Your policy is
Free cancellation for 48 hours
After that, cancel up to 5 days before check-in and get a full refund, minus the service fee.