I should ask my coworker if he tried explaining physical money to him and how he reacted to the idea.
All the kids we saw were capable, I'd even say surprisingly capable, of understanding the basics of stuff like budgeting. I remember we ran a scenario where they're helping a man to shop for himself and his wife, they're pensioners so they have a very inflexible income and an overspend is going to be a huge problem, and the kids were pretty careful, they understood that just because Mrs Smith likes flowers, if we haven't enough money for flowers after buying the intended groceries we shouldn't buy the flowers, they grasped that the choice isn't going to be "Buy both and it'll work out somehow", and that if you don't buy enough food you'll be hungry and so on. Even if all they were doing was telling us what they thought we expected, that's enough, as adults they won't be executed for going bankrupt, it's just important that's a conscious choice.