Wife died and in laws claiming my kid and her daughters money.

Following events have happened: 1. Six months back we had a quarrel at home and after that she went to the police station and tried to file a complaint against my family and me. In the letter she mentioned husband, my mom and my family harassing my daughter and her. Also she mentioned about the dowry. All these statements mentioned in the letter were totally false and when police asked they have put a demand saying I do not want to live with my mother in law but only with husband. Mutually I agreed to make a separate house for both my wife and my mom. She din't file a complaint as her demand is satisfied. This went on for six months. She is working in IT. 2. After six months unfortunately she died naturally at the hospital. Now her parents went to the police station with the letter she has written earlier as part of 1 above and when we asked in the police station they have put some demands: 1. They want all of her daughter's money to be kept in my kids account with themselves as the guardian. Money is really good amount of money as she has several insurance policies. 2. They want to completely take care of the kid. How should I proceed in this case? Please guide me clearly. Thanks.