Husband's mom keeps wanting me to help her sister

I'm a huge people pleaser. My MIL has been calling me to bring food to her sister who lives 30 minutes away. My husband tells me to stay out of it but I do it anyway. Her sister and her husband are both elderly and are not living in good conditions. The house is pretty gross. Last time I was there the husband had shit himself and because the wife is too elderly herself to help him he stayed in it and it smelled awful so I ended up helping. They both seem to have a lot of accidents around the house. The sister has been trying to push me to contact her son for her because he's their only child and maybe he could help them. But they haven't talked in 12 years. I haven't contacted him yet but my husband is telling me to stay out of it. The reason nobody in the family helps them is because the husband is a p3DO. He touched several kids the family including his own son and my husband's sister. He never got a chance to touch my husband because my husband mainly lived with his dad. But my MIL keeps wanting me to help them out. She calls me specifically and I have a hard time saying no.

@Mommaof4 Should I attempt to call the son first or is that crossing boundaries?