All drugs have their pros and cons and responsibilities, and those adults who can keep it from impacting their kids as part of responsible drug use, I don't really have a strong opinion (putting aside the ethics in production and distribution).
However, having grown up with pot smoking parents and knowing others who have similar, I don't really trust the 'it's only after they're in bed' to last many years for those as a pp mentioned who become reliant on it to deal with their emotions anymore than I trust the same remark for any other drug used similarly. Pretty much everyone I know who had pot smoking parents had them either give up doing it in private or just slip up a lot more when they were older. I also think it would be more honest to say it's unlikely they'll need you til the early hours because most parents have stories of an older child who was ill at night needing us.
When my mother chose to stop hiding it, it was awful having to deal with how getting high dropped her inhibitions, how she talked differently while high, and the smell of it - ugh. When I read of parents wanting to smoke pot with their kids, I do feel some disgust as I remember how my mother introduced my brother to it and how she tried to do so with me.
It's legal in many places now and what's worse a angry alcoholic or a stoner whose going to eat everything in the fridge and fall asleep on the sofa
My mother could beat the shit out of me either way so with her it's do you want an angry person who slurs their words while beating you or an angry person who can't stop laughing while beating you. She could have a sweetness and light act on all of those too or while on nothing, but she was a really angry violent person. The drugs didn't make her that way though extended use fucked with her head, it just made it easier for her act that way and feel it was acceptable.
I know another person who when he drinks, he just get sleepy and hungry, similar when around others' smoking pot though it also puts him on edge a bit as it irritates his lungs a lot which actually puts him off food. He's one of the most relaxed people I know, either alcohol or pot just makes it easier to let that all out.
Alcohol doesn't make people angry, it just lowers inhibitions to expressing their emotions. Pot doesn't make everyone sleepy - it wires some people up. I hate when alcohol is put against pot in this way - putting the emotional differences on the drugs, making them responsible for it, erasing the very human element and responsibility in abuse that happens when someone is under the influence of drugs.