@Colleen253 with these maybe ok/maybe disaster situations I tend to message a guest something like: "hey, I'm sorry to be fussy about a pleasant weekend, but ABB insists that I let you know that as far as they're concerned you are the responsible party for the duration of the rental, so if something unfortunate happened after you left, then ABB (& I) would expect you to cover any damage or repairs first and then work out the details with your friends after the fact. It's rare that anything pops up, but it's best to clarify these things on the front end. I'm sure that isn't a problem for you since y'all are good enough friends to travel together, but again, they just ask me to confirm that you know by booking and leaving them behind after you head home, you're on the hook for anything and everything while they're here. It's not our normal reservation protocol to have the "Guest" leave early, but if you trust them then I'll allow you the extra leeway. Also, please make sure they have my contact info and all the house info and I'll need a contact # for them as well just in case...."
or the other alternative is just a quick "no, I'm sorry that won't work"