For my children, my first action would be to ensure that other arrangements made, to avoid them being placed in harms way again. Secondly, I would confront that person without question. These are my children, and without a doubt it is my right and responsibility to protect them from a potentially hazardous situation.In a situation of the substance being used in front of the children, there is never an excuse for intentionally exposing children to any illegal actions. In this case they would only have 2 choices, immediate treatment, or a report to the authorities.
I know this seems tough, but there are situations where harsh reactions are the only onces to get results.
I would do so calmly, and rationally. But I would not just let the issue be swept under a rug. After making it very well known that this behavior will not be tolerated, my responsibility to the rest of my family is to support this person in getting help. I would offer to help care for their children so that they may seek treatment, and emotional help while they are recovering. Their addiction would be the second focus, from there everything else can be worked out. Overreacting will most likely lead to a feud, in which no one will win, the user will withdraw, and the family may suffer. Above all else, the children must have support and be educated throughout this process. They need to be told why this behavior is wrong, why it can be harmful. Not talking about it, will only make them more curious.

Hmmmm....

We commonly see people driving kids around while talking on their cell phones - something which recent studies have shown to be MORE dangerous than driving while under the influence of alcohol (at least for a good percentage of people).

The effects of small amounts of "weed" tend to intensify concentration as opposed to alcohol, which, even in small amounts, causes fuzzy thinking and poor response time. If I had to choose between the two, I would tend to trust someone under the influence of marijuana before I would trust someone under the influence of alcohol.

However, in my perfect version of the world, I would prefer that anyone driving children were completely free of distractions and chemical influences (including cell phones, radios, mp3 players, in-vehicle tvs, caffeine, nicotine, THC, ethanol, or narcotics).

I guess, with regards to the specific question posed, I would talk to the person in question and mention the specific legal hazards and the resulting chain effects upon any children who might be present in the vehicle should the driver be stopped while still in possession. If I felt that my pleas and logical arguments fell on deaf ears, I would simply make sure that my child never rode with that person again. I can't change anyone else's behavior, but I can choose my behavior differently.

I would first drive my children home and then tell them that it is harmful for them. I would also explain them the situation. I would also warn my family member of such actions in future.

Thanks

Yeah, I have had this one happen. One of My family members is a pot head and yeah, I stopped my kids from riding with him long ago. I cannot yank his kids out of the car, but I can report him to the authorities,. They will not pull him over just because I say he is high but he will think twice before he does it again. Sorry but the kids come first always.

My rule of thumb is if I do not do it around my children no one else should, that includes drinking, smoking dope, lying etc..

Even though my children are young adults now, I cannot pick and choose who they ride with. I have to trust the stuff I have instilled in them over the years. Like not riding with anyone under the influence.