Guest check in and after 1 hr returning back and asking to cancel as his Mother in Law can not stay

[Birgitta4]

Hi All
I rent out a superb 1 master bedroom w shower etc in a Cape Cod beach bungalow in Cape Town for selected guests and super enjoy my visitors. I got a lovely enquiry from a married couple 2 months ago and approved, and then a week ago he sent a query that his wife wanted the Mother in Law to join. Could I host her ? I responded that I unfortunately do not rent out 2 bedrooms but will check, and did some recommendations and they found a place for her 4 km away. 
They now all arrived at 1 pm and loved my home, checked in and then went out as Mother had to go and check in. 
1 hr later they arrive back saying that the place can now accommodate them as well ! so he wants to move as Mother don't want to stay alone. I asked if my place was bad, and nope, was all about the Mother. Flip. 
I told him that he has technically checked in, returned an hour and this is not something I can accept as peak season so he must pay to me full price. 
Bad planning from them 
He said he understood, took there stuff and sad that he and the wife might return as they liked my home, and the Mother might change her mind. 
Poor chap but I will certainly not pay a penny back, regardless they stay. 
Your input please.
Best

Birgitta

[Linda108]

Just let the guest initiate the cancellation and do not agree to it, @Birgitta4.  The refund will be processed according to your cancellation policy.  Since you had a conversation with the booking guest confirming there was nothing wrong with your listing, I suggest you summarize the conversation in a message to the guest directing him to Air BNB to cancel the reservation.   You need to protect yourself from the guest complaining that your place was not as advertised and seeking a refund.   Good luck and let us know how it all turns out.