@Maureen356 When accepting the reservation what steps do you usually take to vet guests? Do you require positive reviews? I see that you have self check in. Is it possible for your co-host to greet the guests for check in? Do you have any cameras on the property at the door to monitor that there will be only the 8 guests?
Perhaps you have already thought of this, but I always wonder why a host would want to have so many people in the house in the first place. You have 3 bedrooms so 6 is a reasonable number. Adding extra sleeping arrangements encourages more people to share the expense and thus encourages a level of hard wear and tear even with good guests. Do you charge for additional guests over say 3? Again discouraging bargain hunters.
I gather the age of the group is the most concerning to you, right? What about the reason for the reservation? Birthday, wedding, or othr celebrations usually encourage drinking. Also, where are the guests coming from? Are they local...often not a good sign.
While it is not fool proof, establlishing a rapport with the booking guest is important. Tell the booking guests of your concern about the care of the property and how prepared the booking guest is to maintain respect for your home. See what kind of response you get and that will help you decide. Good luck!!