@Toni211 Definitely do not accept this. It is in fact a party. If you have no party rule in your listing, you can tell them that you do have no party policy in place.
12 people and eating could have caused big mess and a lot of trash to be collected. Recently a guest lied to me and had a party in my house, even though they had collected all trash and took with them, but they still left a very dirty oven with a lot of grease and burned food at the bottom. It took 2 hours to clean the oven alone. There are food stains on the kitchen floor, which is very hard to remove.
Not to mention that they used up all my kitchen supplies of napkins, plastic spoons, cups, plates, etc.