Are you and/or any of the other ladies really good at disguising yourself? Seems like that could have some potential.

For Instance: Instruct your victim to go to a certain bar. When someone comes up to him and asks XYZ (i.e. some phrase you pick that is both weird and sexual) he is to respond in a clear voice QQQ (some other phrase you pick that is even weirder and embarrassing) then they leave.

Pick a bar that is known as a gay hangout though not telling the victim that. If the mistress picking him up can convincingly disguise herself as a man it could be fun.

Alternatively disguising the mistress as a nun or a granny might be interesting.