FWIW I, even being childfree and having no horse in this race, find this problematic. For many of the reason already mentioned.
Children emulate adults. They are, with or without adults, going into a store that looks like a pharmacy, dispenses candy like a pharmacy in what looks like a sterile clinical environment.
When a doctor or dentist gives a young one a lollipop or such for being a brave patient, I don't think the child is going to associate later on the candy with the doctor experience.
However, visiting an entire store where all the environment says is "medical" and all they dispense is candy, well, I see that as direct association. Kids aren't known to be the most rational of people, so I'm not going to put adult reasoning into this.
Years ago, at our monthly regional meeting, I made up a gag thing for the attendees, who were almost all nurse managers. It had been a stressful quarter, so I found just the right color blue jelly beans, put them in a jar, and labeled it "Valium PRN"
It got a laugh from everyone, and the jelly beans were pretty much gone by the end of the day.
But this was a room full of adults. I never would have presented candy to children as a medicine. Why? Because it's not.
Regardless of what "happy pills" connotes to anyone here, the word "pills" is right there. Pills aren't candy.
I mean, weren't we in the first place all taught that growing up?
Pills aren't candy.
Another problem I have is that I feel there are so many better ideas out there. Why this one?
There's a store here in a trendy area called "Big Top Candy" It's been there for years, and is a great place to go, even if you don't eat candy.
Rather than being lazy and just putting various colors of candies in jars and calling them "pills", they bring back candies from yesteryear, that even young people get all excited about.
And yes, they do have candy cigarettes, which in the setting makes it seem quaint, in that it's so obvious in it's silliness.
A former co-worker was once reminiscing about how her beloved grandfather would give her sen sen gum and violet candies.
I went to Big Top after work, found them both, and gave them to her the next day. She got all teary holding the package of violets up to her nose, because she said "I can smell my grandfather"
I just don't imagine evoking that response giving someone happy pills.