First, be very careful before you pre-approve a guest. Ask more questions, find out more about them. Make sure your guests are properly verified.
Second, make sure you're ready to host before you go live, which means making sure your place is ready and your settings are as you want them to be. In our settings, we don't allow same-day bookings. If you set yours that way too, then the Airbnb platform won't allow the booking to happen and you won't be caught in this dilemma.
Third, if you pre-approved the guests and they haven't accepted, then go ahead and withdraw the pre-approval if you're having second thoughts. Let them know you aren't ready and suggest they find other lodging. If they accepted your reservation, then their phone number will appear. Telephone them to clarify what time they will arrive. Check ID upon arrival and have someone with you since it is past sundown.