Holy crap, that is just so horrific. It is so sad that people who can not even afford to clothe and feed themselves are cranking out child after child.. so so sad. I am very glad that things did not end tragically there; you're just an innocent woman driving down the road, and something like this happens..
I would call Child Protective Service; they have an obligation to investigate things like this, and every so often i see "houses of squalor" on the news because someone called and complained.. then it would take some of the mental burden off of you I would think, and ensure that someone with government power did something.. sadly, even if the kids ended up in foster care, how much worse could it get for them?