There's no dancing (except for the horizontal Tango), but apart from that, and the fact that there are people shagging everywhere, it's a fairly nightclub-like atmosphere.
Be aware, though, that a lot of the action is pretty full on. For a guy, things can be quite measured and you can choose when to join in and to what degree, however, it's a bit different for the ladies. Any new girl turning up and making signals that she's available will be pounced on by a large crowd of blokes given half a chance. There are a couple of areas in the club that are semi-private, but even then you're going to find yourselves surrounded by a crowd. Don't go to insomnia hoping to meet other swinging couples; that's not the way it works in the main.
I wouldn't want to put you off as it really is a great place, and a real eye opener if you've not been to anything similar before. I'd suggest a visit just to check things out and sit and watch first to see if it's your kind of thing. Your lady may get a lot of polite requests to join in, but there won't be any hassle. I'm strictly a one-pop-a-day guy so I spend a lot of my time there just watching and seeking out opportunities for a bit of OWO, so you can pick and choose what your activity level is without being concerned about anyone else's expectations.
Good luck