I understand your fear and reluctance, however you have a responsibility as a parent and as the person who brought this women into their lives. Are you afraid of legal action be taken against the women? Or are you afraid of putting your family and extended family through such an embarrassing and traumatic ordeal?
My suggestion would be to find a lawyer and discuss those fears. They know therapists, and people who can at least guide you on how to proceed or what warning signs to look for ...as far as behavior from the boys.