Be sure to have a Safety talk with all the youth participants. Horseshoe is quite a safe sport by nature, but because the sport entails throwing chunks of metal in the air, there are some clear hazards that should be addressed.
Be sure that the youth never throw horseshoes at one another for any reason. Those pitching horseshoes, and their non-pitching competitors, should each be aware of where the horseshoes being pitched are. No one should stand directly behind a participant who is pitching as the back swing could hit them. Other youth, coaches, and spectators need to be watchful in case a shoe bounces off the top of the stake or off of the cement around the opposite horseshoe pit. A protective barrier (fencing) should be placed around the pitching area to keep people out as much as to keep horseshoes in.
Care should be taken around the stake and backboard. Be sure to instruct the youth that no horseplay is allows near the stakes and the backboards are a potential tripping hazard.
Some horseshoes have soft metal that may burr and become sharp. Be sure a small metal file is available to smooth these off to protect hands and fingers. Some youth may choose to wear gloves as they pitch.
Generally, horseshoe are played outdoors. Be sure to encourage protection from the sun (hat, sun glasses, sun block, etc). Be mindful of storms; lightning and horseshoe pitching do not mix well.
In spite of these safety hazards, the low-impact nature of the sport should preclude most sport related injuries that plague many youth sports today.