Father behaves inappropriately towards son's wife and other women

How should I respond to my dad's inappropriate behavior toward my wife and other young women? I've expressed my concerns to him, but he says this is just the way he is and that he has no intention of changing. I've decided it would be best if we don't spend time with him anymore, but this devastates my mom; she still wants to see us. My wife says she's willing to make the sacrifice by enduring my dad's treatment, but I don't want her to do that. How can I protect her dignity without depriving innocent parties of a desired relationship with one another?