So, I talked with some old friends, that through the years, could answer through their own experiences, including myself (though, I declined).
One is gay having a nice dinner party with the two that he wanted, and then talked over a night cap with the mentioning of a movie, this being the Porno movie. As the night progressed they two indulged.
My other who was bi-had his eyes on two different people and yes, guy and girl. They went on a weekend trip and found themselves with one large kingsize bed and loads of fun...but again not too sure what sort of threesome your chatting. Consideration of positions, for that can bore people without the chance to try something, instead of becoming a library, so to speak.
Now:
my nearby experience, over 25 years ago.

A gal that I'd worked with (nice blonde, big tits and ass) wanted to experience life's pleasures, being that her man was a somewhat rocker type aka Air guitarist. We had come back to my place, after having breakfast and yes she had rented a porno movie...I wasn't into either, especially him, and she with her choice,but if you want to try this LATE night attempt ...and I do mean late type night then consider being tired, but coffee can come into fun. Laid back with a comfortable bed, porno movie and good company all seem to work well together.
Though some say too tired to do
many positions or open to too much exploration, but a well beginning.
Good luck! Hopefully, you have those truly interested.