If you know a mother that carries her child around to homes and smokes pot on front of them what should one do?

Your words against the opposition can be debate a video speaks for itself it adds more credibility to your words it's up to you which agency you report this issue to. I think if she is willing to accept help from a religious institution someone that will minister to her and guide her in making a choice to go to a rehab most congregations have people that volunteer to keep children while the parents are resolving issues like this one of course with the parents permission and their signature for temporary care for their children

You can always contact Social Services and make a report. You can give your name or it can be strictly confidential. However, you need to have the name of the individual and where she lives. Also, you will need to contact DSS in the county that she lives in. That is pretty much all you can do except call law enforcement who will in turn possibly contact DSS.