hosting at home, the sheets question and the bedroom assignment thing

right so weve always met at hotels or gone away to cottages but this time were just hosting at our house in manchester for the saturday night, two other couples coming over for dinner and stay. semi detached, three bedrooms. and now im in a tizz about all the practical stuff that nobody ever talks about. like... do you put fresh sheets on every bed obviously yes but what about the actual MAIN bed where the missus and i sleep, are people gonna be on that, with each other, with us, all of the above. do you assign rooms or let it flow. the spare rooms have a double and a single+double bunk situation which is silly so really only two proper guest beds. how do you not make it awkward when you basically have to say "one couple in the spare, one couple in our bed if things go that way, we crash on the sofabed" or whatever. anyone with home hosting tips, ive googled and its all about clubs or hotels