It's a beautiful summer day, and the neighborhood kids have gathered in your backyard for a pickup game of baseball. The only problem is the age range of the kids who have come out to play. The oldest are 12 and the youngest are only 4. Older and younger kids have very different ideas of what it means to play backyard baseball, and they trigger very different safety concerns.
Older kids have faster reflexes and more experience being around swinging bats and fast-moving balls. You generally don't need to tell a 12-year-old to stay far away from a swinging batter or to not take practice swings close to other people. But this might be one of the first baseball experiences for a younger child. They need to be told when they are too close to a batter or in danger of being hit by a foul ball.
The best idea is to play backyard baseball with kids who are roughly the same age and experience level. If that's not possible, stick close to the smallest players and make sure that everyone is keeping an eye out for the little guys.