Remember that these are not strictly refereed games, these are pickup games for fun. The game is the best teacher!
If we have a large enough turn out that we need to run some separate pickup games because not all the players can fit as guest players on existing teams, then Game Supervisors will set up a coned off field and run a jamboree pickup game. Ideally there would be no subs -- everyone should just play. If there are subs, parents should be present to supervise the subs and the game supervisor should try to make sure everyone gets roughly equal playing time.Follow the U5 Game Supervisor protocols where you play a 20 minute game and mainly keep the game going or whistle if it goes way out. For more information see U5 Game Supervisor.