You don't have to bring your mattresses or sleeping bags. But it would be a good idea to bring some alcohol with you. Because here it's super expensive! And I guess that we could drink a bit?? You can decide.
And, one more thing: I hope you don't mind that some other people will also come to the cottage. I don't know if you want to spend the time there just with us or should I organise something bigger (=more people)?

That's my info paggage now,
Eleni