"And I know that thinking about what he and I will be doing will probably get your little willy hard -- so it's fine with me if you indulge in a couple of hand-pussy quickies while I'm out. My sister said she was sure that's what you'd want to do, and it is -- isn't it, hun?"
I don't think my wife has slept with any of my friends, anyone from my office or any of our neighbors. However, I can never be sure because we agreed from the start that she can have sex with anyone she wants and doesn't have to tell me anything that she doesn't want to. To be honest, the uncertainty turns me on.
You had always loved your wife's smile -- and at this moment it was her way of welcoming her date and letting him know, as he approached her, how pleased she was to be going out with him.