I don't really know which is the protocol in a swinger's club, but I've read that single men are not very well received. I'm really curious about that, but as far as I know there isn't any club near my area. So, I'll be still curious for a long time!
Regarding the sexual "roles", I like to switch: sometimes I like to be the dominant one, feel that she is my fucktoy. But other days I'm there for serve her desires. Kind of schizofrenic, but I think is better that way or, at least, more varied!