Can I get full custody of my children if the grandparents are capable of abuse?

I may be going through a divorce and want to seek full custody of our two children. My in laws have a family history of child molestation. My husband's parents do not have a problem having these child molesters over or around my children. When my sister in law told her parents (my kids' grandparents) about how she was d by a family member at age five my mother in law's first reaction was "Was it your father". My father in law has frequent mood swings, sometimes violent. They lived in our backyard for five years and I have witnessed his behavior. Because of the family history of ual abuse, his tolerance of certain family members who have ually abused children, his mental state (I have proof of a family mental illness), the fact his own wife may have thought that he could have d his own daughter I wonder if I could win sole custody of my children if I divorce. I do not want to totally keep his parents away from our kids, I just want to make sure the visits are supervised. I am only staying married so the kids so they are not left alone with the grandparents. What can I do? I know I need proof but what if some family members are not willing to testify for me?