I deal with this issue a ton, and airbnb doesnt do anything to help.
For whatever reason my place attracts people who want to throw "game nights".
These game nights ALWAYs have 2 people as the reserved guests. These people sometimes bring upwards of 20 extra people. I state on my listing you cant bring extra guests, anything over 5 people and you will be charged $545 (my group rate) 1045(if they want the backyard as well).
That stopped people from trying it until airbnb took my listing down for basically advertising parties.
So now i had to create another listing and inquire each and every time about the purpose of the stay.
If someone brings a friends or two fine, i see it and ignore it. But not if theyre throwing a birthday party, not on my white floors.
My stay is the full apt but we own the entire property and im usually right upstairs overlooking things. If i didnt live here there wpuld be endless 2 guest stay parties.
Airbnb intemtionally ignores this issue.
If i were you id have a simple rule like: each overnight guest is allowed 1 extra guest during the day. Each guest after that must be paid for
So a reservation 2 people can at worst be 4. But even then when they break the rules bnb does little to help