When boarding more than one dog overnight, what sleeping arrangements do you use?

I never leave more than one dog uncrated at night. My dog is always crated, but my guest dog sometimes is, sometimes isn't, depending on what that dog is used to. However, if I have two dogs, then I do crate at least one. I think, for their safety, and considering I don't know their behaviors well, its better.

It really depends on what you want and the dogs themselves.

I don't crate dogs. However, I have had customers bring crates over for their dogs, which is fine with me. I do have several dog beds that guests can use. For the most part, dogs have free access to the first floor of my home, so no dog sleeps in my bedroom, not even my own. They've all found comfortable places for themselves. If I've ever had to keep dogs apart, then I've used baby gates in the hallway, so that some dogs have the front half and the other might have the back half of the floor. But in most situations where I've had three or more dogs at a time (holidays typically) everyone has gotten along.

It depends on the dogs. The first two days I separate everyone at bedtime. I ask owners before sitting if its ok to crate there dog or leave them in 1 or my 2 spare bedrooms. Everyone I have asked didn't mind. After the second night depending on the dog I would. Example my german shepherd did great with another female shepherd and they would cuddle together at night but I gave them the first two nights alone so that they could get to know each other and I'm home all day and pay close attention to how they react. Example 2. My german shepherd did not like a Chihuahua because she would bite my dog all the time and run off. Its the breed so I could not let them be alone. Especially after the dog nipped at my 4 year old and my shepherd was ready to hurt the little dog after nipping our child. Ask owner and give them space at first and go from there. Dogs always act different when there new people and places around.

I never leave dogs together unattended at night for safety reasons.
Everybody must be separated at night, because it takes a second for an accident to happen, esp if the dogs do not know each other. I do not let dogs sleep in my bedroom but I have a separate study room where I also have a bed, so I take one crated dog there, the other can be without a crate and I close the door. My own dog sleeps downstairs. And I had to board another dog, then I use a private dog room and close the door too.