Mutual Agreement for Divorce

I married as per Hindu law in February 2002 and having 2 Children (1 Daughter and 1 Son) and now I and my wife living separately since June 2011, The reason was my wife had extramarital affairs and residence of my colony caught them and took a written note from the man accepting his relationship with my wife and all residence also signed that note. I have only copy of that note with me. After one week, my wife left the home with children. After one year, she complaint in Women Cell but return back her complaint on 2nd hearing and also left both children with me in presence of his family at my home. After that we never meet. Now I want Divorce but she requested for out-of-the-court agreement/ procedure/ Affidavit that both can sign and keep it as a legal document. She told that she can signed any document related to divorce out of court and don't want to go in court and requested for mutual agreement out of court. But I want to go as per law but confused for (a) As she asked for mutual divorce and also said that she will not claim any amount on account of maintenance for herself and also she is not interested in children. As she already having one child (which I don't know, either her own or she is look after). If I filed case for divorce under mutual agreement and later she denied, Can I again filed as per extra matrimonial relationship. Please advise