@Rachel1842
There is a simple solution. Install a digital lock, they are effective and simple to use. I show all my guests how to use it...
1 - To lock the door press the lock button.
2 - To unlock the door enter your 4 digit code (usually last 4 digits of the phone number on the reservation, who forgets their own #) press unlock.
In case the battery fails, we have a physical coded lockbox, they can text us for the number. We will them replace batteries asap.
No way our guests can get locked out.
Hope this helps.