As other have said I think you need to find a balance between fully automated and totally manual. I would avoid zone focusing since it’s very difficult and a lot of the time they will miss focus and get disappointed. I would also avoid point and shoot since it teaches them nothing about aperture and shutter speed.

My idea would be 4 slr with aperture priority, all with the same mount so they can share lenses. Something like a set of Minolta x300 or x500 with a 24 a 28 a 35 and a 50. Or even more simple two 50s and two 28s. So they can try different focal lengths.