I will not be available to welcome my guests. What should I do?

If you have someone else available to do the check-in for your guest, make sure you inform your guest of the situation. They may otherwise be a little confused.
If this will prevent you from hosting your guest, please make sure you inform them straight away so the booking can be canceled from our end, and they can get a full refund.
You may want to explain to them your reasons for being unavailable and reassure them that the check-in will present no inconveniences. Reassurance is key here!