I've told them they're allowed to pick as many dandelions from the lawn as they like. Like many things they do, their enthusiasm is endearing. Their perspective on the problem is limited to what they can see: a flower.
I see a little farther, where the weeds will spread through the lawn, and steal the water from the grass during the hottest parts of the summer. I see hours of pulling them up from the roots, to slow down their growth.
A shift in perspective can be a powerful change. Even when you recognize an obstacle, sometimes it can be quite refreshing to consider other perspectives, and other objectives to judge merit. The world is not black and white, but shades of all colours. Sometimes the green may be covered in yellow, but that's not always a bad thing.