This is one of the problems that I think you can actually prison your way out of.
If a minor is ever found working in a place they’re not allowed, every manager who has ever worked at the same time as the minor goes to prison for 20 years, along with 3 levels of bosses above them. Like the made up thing about North Korea imprisoning multiple generations of your family, but exclusively for management. Make it so the consequence of not reporting a child labor violation is so incredibly high for everyone who’s even nearby that regional managers start showing up to check because their life would be ruined if they didn’t find it.