It's not only me who keeps an eye on them; it works in both directions: usually it never takes long before they ask me about what I'm doing.
It amazes me how good kids usually are at identifying plants. Once you show them how plants look, they know what to look for. We have taught our kids though to always check with us before they put anything in their mouth, but we never had any problems.
While I harvested two large bags of stinging nettle, my son picked some baby cleavers and my daughter some sorrel. Then we picknicked and had some daisies as dessert. After their nap, we hung some of the nettles to dry for later use (nettles are a staple food in our family) and the rest we combined with the cleavers and sorrel for a delicious spring soup.