Are coaches meant to stop children taking the same restart every time?

I would share the restarts around a little. Player ownership does not have to mean the quickest child owns every ball that goes out. If one player has taken five in a row, a simple “let somebody else have this one” is not overcoaching the football decision. Then step back again and let the new player choose what to do. You can also build the habit in training by asking the nearest player to restart rather than the loudest or quickest one. I would not create a strict rotation where the adult counts every restart. Just notice if the same child is dominating the opportunity. The format is supposed to give all three more decisions. Restarts are part of those decisions, so it makes sense to protect access to them.