How do I deal with troublemaking staff?

I have a couple of directors.who are troublemakers. They have whipped up several other directors and they together have gone to my president making all kinds of allegations against me - 95% wrong. BTW, I supervise these directors. My president wants to moderate a session where they tell me face to face what they don't like about me. I have been very good to these folks (promotions, pay raises, budgets, professional development opps, participative management, very complimentary, etc.) and am stunned they have turned against me and like I said most of what they are claiming is flat-out not true. I want to be a professional in this "mediation" meeting - calm, collected, and a good listener, but I am very hurt. A few of them at least would like nothing better than to see me lose my cool. How should I face this mediation session? The format = 1) they talk, I listen; 2) I respond to what they said and then voice MY concerns; 3) We talk about how to move forward positively. A couple of these folks I thought were my right-hand people. Like I said, I am stunned? How should I approach this? I can tell by the way a couple are acting around me that they seem to feel guilty for what they did. I am at a loss.