I want to confront parents that I see smoking
Oh really? What will you say to the parents?
I am not sure yet, but it will be stern.
Trying to direct the actions of others that are not bothering you is disrespectful. Telling others to stop things that have nothing to do with you makes no sense.
I think it will be best if they just stop now.
It really would be ideal for parents to not smoke at all, but it's none of our business on what we can do. It's their lives, and not ours and we have to respect that. How about volunteering for more regulation or awareness on the harm of smoking, it can indirectly get them to stop.