We are really in the discussion phase of this. The best solution might be a completely open marriage were we don't have any physical contact with the others secondary partner. We are just exploring this as a viable option. We would not expect this other person to bear any responsibility when it comes to our home life if they do not wish.
My wife has not been with a woman in almost 10 years and this could be something that turns out a disappointment for her. We are just trying to prepare ourselves for the future. I want my wife to eventually open up to her family but I know that will be a big battle for her. My family is more accepting of things like this. My parents were swingers for several years before they got divorced. Her family is heavily involved in church and are very judgmental of everything we do.