You could get them to initial something when they leave an area? I have never seen this in practice but heard it works in some settings. Maybe a wipe-off board in each area? It does sound sensible; I did get sick of hearing that all my child did was junk model for the whole of the reception year. Maybe if the staff had monitored, even just for a while, it might have spurred them on to ensure somehow that each child did more of a variety of things.