Man. Good on you for coming here to ask for advice. It is a delicate matter - what with not wanting to potentially embarrass the guy, and with her being boss's missus. I'd either take her quietly to one side and say you think it's dickhead behaviour. Bullys are seldom ever brave when they're alone. Or, the next time it happens make and face and loudly voice that it's not funny. Say that their craic is pure shit, and they need to get some better jokes. Call them boring. Embarrass them.