Hi, You are not late, I have only just started to sow and plant up this week, the soil where I live has been too cold. (North Wales). I have planted leeks in trays last week and they are just coming through, I have lettuce in trays again planted last week. The only things in the ground are early potatoes and onion sets I planted this weekend. I would go to your local seed suppliers and grow what you like to eat. When our children were young we use to give them things like radish which mature quickly and keeps their attention, then add them to salad so they feel they have contributed, we also use to let them grow mustard and cress on the window sill to inspire them, perhaps also some lettuce. They use to also always help with collecting the produce, our daughter still grows today, at 30. Hope this helps