@Scott2084
That's quite a situation!
As far as liability is concerned, only your business insurance agent can give you a valid answer.
Fees? Seems to me that this guest wants to use your entire property for a party, for the cost of a room in your home for 2 nights. Imho, better she should hire a hall that is set up for events, and peacefully stay in your Room.
Btw, Our House Rules states that we don't allow parties, events or visitors, per our business license regulations. Our guest limit for our Room is 2 people.
Personally, I'd not agree to hosting this event. Our county business license wisely forbids it. What does yours say?
This is a whole lot of people, That could cause an enormous strain on parking, plumbing, the acreage. Anything can happen with 20 children, a pool, pond and hot tub; and distracted adults.
Do please let us all know what you decide!