Hi Margaret,
That is a really frustrating situation and I can understand cancellation is not an option for you becaouse of the penalties.
Instead of canceling the reservation you could send them an alteration with a check out for tomorrow. Simply tell them that a family matter has come up and you will need the space.
If you want to make any changes to an existing reservation, you can send your guest an alteration request. This will allow you to adjust the dates or price of an accepted reservation, modify the number of guests, or switch the reservation to another one of your listings on Airbnb. Simply go to Your Listings > Your Reservations. Find the reservation, and click on the Alter or Cancel button. On the next screen, head to Alter Reservation.
You’ll be shown a subtotal, which you can adjust according to your needs. Be sure to enter a number with no symbols or spaces, and make sure the price is inclusive of your nightly rate, cleaning fee, rates for extra guests, etc. (just like a Special Offer). The subtotal is the reservation total before Airbnb service fees, which are then adjusted automatically according to the new reservation subtotal.
It’s important to remember that any alteration requests you submit are always subject to availability and terms and must be accepted by your guest. If the alteration is accepted, the cancelation policy is updated according to the new reservation details. At acceptance, your host payout will be updated and the guest will be charged or refunded according to the change in price. If the alteration is declined, the original reservation details remain intact.
Check this article on the topic: www.airbnb.com/help/question/50
I hope this will help you. Good luck!
Slavica