The nice thing about such basic hand tools is that you usually get to learn from mistakes without permanent consequences. Will a child hurt themselves at least once with a saw and a hammer? Probably. Will they seriously hurt themselves? Probably not. Will they learn to not hurt themselves? Almost certainly.

I also don't remember how exactly supervision works, but it definitely isn't just dumping a bunch of kids at some unattended construction site. Parents and/or the team managing the place are at the very least nearby.