Two young person projects:
1., The weeding primer: I planted carrot and radish seed together on a bed with my eldest. We sprinkled on some dry grass clippings and watered.
As radish came up we would weed briefly to start. As radish got bigger we could weed a bit longer (still only a few minutes at a go). Soon radish were big enough to eat direct from the garden, and weeding had a pay-back that made slightly longer sessions work.
About the time all the radish had been picked out, carrots were coming on. They would need to be thinned (and eaten too). I had regular competition in keeping the carrot bed weeded-eaten.
2., Go big: nothing says gardening like going big. Be that a 20 plant block of sweet corn or a four some sunflowers. Pride of ownership can start early. Just keep the chores brief at the start.