For the tweens and teens, it’s an opportunity to see how working works and show they can do more. For retailers, it’s a chance for publicity and showing potential future workers it can be a good career.
Have the young adults apply for different jobs at the stores. Interview them and pick the ones that fit. Then train them little by little (could be a whole semester’s course), then have a day or a week when they operate the store (with not so visible supervision.)