Would a notarised personal agreement hold water in a court of law?

My daughter is coming to live with me. Her father and I have negotiated a personal agreement between us. He will not put her on the plane until I send him this signed, notarised agreement that I will not seek custody for one year. ( and some ridiculous conditions, too) – she is so desperate to leave and I am so worried about her I would sign anything. She has told me of incidents of drinking and violence in their home, so I do plan to sue for custody. Could this agreement that I signed be given much weight?