OK, @Pete28 and all of you lurkers (58 views and only @Jessica-and-Henry0 had the guts to BARELY respond???), if people didn't have sex, YOU wouldn't BE HERE, right? None of us would. We should be grateful for sex.... and it can be a bit 'messy.' There's the 'rub' (forgive the pun!)
THAT SAID,
If your guests are sharing your house, you may have something in your house rules... something like a curfew? Lights out and quiet time after 10pm? Make the house rules and your personal presence enough to discourage 'inappropriate' behavior?
Keep in mind that most guests (couples) will have a bit of 'vacation-brain' going on. Not their place, right? Let go a bit? The kids aren't around... and they've rented the space--to whatever degree you've stipulated, in writing, or otherwise.
If your guests have the place all to themselves, this is a completely different scene, and one you have absolutely no control over.
DNA is powerful... deep subject, eh?
Best,
Kim