As others here have said, you and your husband both know your kids. It’s likely they are already sleeping with their boyfriends/girlfriends if they are bringing them home for the holiday, and if you ask them to sleep in separate rooms, it invites a bit of sneaking around in the night/dishonesty.

I think the other side of this is are there enough rooms to split everyone up? If I was visiting my boyfriend’s family and they asked me to share a room with my brother’s girlfriend, or sleep on the couch because we’re not married I would be super uncomfortable.

Personally, the first time I stayed with my now husband’s parents, they set up the guest room for us to share no questions asked. We moved in together after our first year of dating, and were married after four years. But my own parents expected us to sleep separately until we were married, even though we lived together. Whether they knew it or not, we just waited until they went to sleep, and then bunked together anyways.