Hello @Syd351
One thing you must NOT do is cancel any of these bookings. You can ask the guest to make an alteration to their booking and here is the Airbnb link you can send them:
https://www.airbnb.co.uk/help/article/1363
Changes are possible within your cancellation policy and you have to approve the guests request. Read this other link and it will explain how this change could affect you:
https://www.airbnb.co.uk/help/article/913
If the guest can't manage to change their booking, you can alter it from your end but as there is that second booking and I don't know if it falls within or outside of your normal cancellation, I would let the guest make the change from their end. They will see automatically if they are able to cancel free of charge or not. If it is, then all is well and the dates on your calendar will free up automatically too so they will be able to use the first booking to come a day later and extend the reservation using up the freed up dates to make just one longer booking.
The difficulty will arise, if they are outside of your cancellation policy ...
Good luck
Joëlle
