@Suzanne302 My feelings and beliefs, together with actions completely!
A first-class attitude to what was obviously both an emotional and embarrassing situation for the couple, who sensitively asked what they did.
Of course, what @Sarah327 decided to do is up to her, but having been in an 'emergency' situation myself once, I know only too well what it will have meant to the Guests.
There is - of course - another possibility, and that is for @Sarah327 to contact the Guests, saying how sorry she was to hear about their having had to cut short their stay, and that whilst in this instance she isn't able to refund anything, she'd be more than happy to welcome them back at some other time, and to say she'd reduce the price to/for them then.
Maybe she could also "throw" in a couple of little mementos as well, for their return visit, so that it would still be memorable for them, but for a different reason?