Kate's place is the best in Port Campbell with that price range. Can accomodate big group, great location, and can be booked for 1 night while many other properties request 2nights minimum stay.
The minus point is only the number of toilet & shower, which is only 1. But it is cleary said in the description. So you should be aware of it before make the booking.
Overall, it is a very good deal for a one night stay in Port Campbell for a big group.