As you may have read on another thread, I had my first introduction to an off-premise club last weekend...but it was surprisingly laid-back and there wasn't any pressure from the guys there that I could detect. A lot of overt staring, yes, but then I was running around topless and bald twins tend to invite attention

Since you're going as a couple, I think the chances of something bad happening are slim.
But I also believe the atmosphere in any club probably varies each week based on the patrons, the theme (this club I attended has frequent and varied 'theme' nights) etc. You might want to ask folks who go there regularly which night is best for newbies.
I might add, my partner and I had agreed beforehand that we were just going to chat and observe others last Saturday, but we had a chance for a FMF threesome fairly early in the night. In this case, it was a woman who made it clear she was interested in us both. Neither of us was attracted to her so we just stayed polite but didn't invite anything more. She tried to pick us up three times during the night. I guess she was what one would term an "assertive bi chick" rather than an elusive hot bi babe!

Now I realize this may be many couple's dream, but we would rather proceed with the right person, rather than grab anything we can get.
Good luck and have fun together