Informing one's husband about father in laws illicit actions

My friend needs an urgent advice on the following: I am living with my in laws in a big house, my father in law and mother in law live in separate rooms, they do not have any physical relation. My married nand is also living with us as her husband is in saudia. She is a working woman. When she goes for work , my father in law takes her 3 year old daughter and I have seen him doing real bad things with this girl. My other two dewranis have also seen him doing bad stuff with goat that we have. Two other minor girls of house are also witness that their grandfather touches them on private parts. If I inform my husband, or any other person at home, I fear divorce. I am already divorced and this is my second marriage. These people are very far away from deen, they think the father is pious and can not commit any sin. If I don't tell, I feel guilty. What should I do?