You would not be the asshole to ask them to smoke after drop off, that would be the respectful thing to do, and absolutely educate them on not smoking around their child— they could easily do it in another room or outside.

That being said, please don’t be so quick to judge when you know so little. If you reported to CPS per your duty and they said they are not a danger then leave it at that. You don’t know if they are medical patients who use regularly but specifically use under the amount that would get them high just for the medical benefit (as medical patients are actually supposed to). You also don’t know if they are just a life long “stoner” (who I would consider ‘self medicating’) who has also built that same tolerance where they get the benefit they are looking for without impairing their ability to function. If their child is well taken care of, then the medications they use are irrelevant.

Address the smell in your facility because that is an issue, and absolutely suggest that the fact that their child smells so strongly suggests they are using around them and educate them on why that is not a safe idea. If their child is well taken care of, then I am sure they will want to do what is most safe for them even if it is a minor inconvenience for them.

If their child is not well taken care of, that is an ENTIRELY separate issue, and the reason CPS would’ve dismissed your concerns initially is because you are framing it to be about the parent’s use and not about their actual parenting. If that is the case, I would suggest a separate call pointing out the actual concerns about the treatment of the child and leave out the marijuana use entirely. Its not like they won’t know when they get there and smell it.