Problems with Mother-In-Law?

When we visit my husbands step-mother and his dad she yells at my kids constantly finding fault in everything they do. She makes it quite clear also that she doesn't want us there when we do go over there. She will turn the tv on and watch her show when we are sitting there or get up and go sit downstairs. She acts very moody with us. There has been other instances also. She has also said that she is putting away toys for her grandchildren meaning her own sons future children, as she doesn't see my children as her grandchildren. This has been going on for years and I am sick of it. I don't know what to do. My stomach gets in knots going over there and I hate her yelling at my kids. My husband doesn't want to say anything to her or his father about anything either. He agrees she treats our children rudely but doesn't want to upset his dad or her. But he doesn't seem to care about my feelings and wants me to continue going there as if nothing happened. What can I do?