Coach Tom Bass, author of the books: Football Skills and Drills, and Play Football the NFL Way, and defensive coordinator of the Tampa Bay Buccaneers under John McKay once told me at a coaching clinic a handful of years ago that the best advice he could give me as a head coach was to never allow a father to coach his own son.
He made it a point to recommend to me that if I had no other choice and had to have fathers coaching out of necessity - that the responsibility of coaching for those fathers in question was some other position than the ones their respective children played.
Why was a coach who literally wrote the textbooks on coaching modern youth football so opposed to having fathers coach their sons? Coach Bass explained it to me this way: "Every parent believes their child is the most capable, best player on the field - and that is OK." But you as a head coach have 22 positions on the football field to fill and 30-35 players to do it with. A player - no matter how good - cannot play two positions on defense at the same time nor can that player be responsible for two positions on offense at the same time. Thirty players cannot all play quarterback or running back. And if a parent is coaching his child, that expectation will be there to some varying degree in the form of favoritism or nepotism.
Moreover, Coach Bass went on to note that fathers who coach their own sons have little real value because fathers tend to be harder on their own children. Often times, they are short with their children when they error or yell at their sons when they fail, which limits the benefit of their coaching or even negates it entirely. It also lessens the capacity of your own coaching points because a father always trumps a coach, and it is certain to have a negative affect on that child's playing ability.
In psychology, there is a branch of analysis called the "Affect Theory" and three of the cautionary negative affects: anger in the form of a clenched jaw, disgust in the form of a lower lip raise, and shame and humiliation in the form of a head down, all negatively impact optimal mental health. And as a parent whose children play sports will attest, these "affects" are all commonly found at youth sporting events.
Criticism is important because it acts as a rite of passage from youth to responsible adulthood. But if you are a father who is a coach, the criticism lines tend to blur and that confusion can be detrimental to a child. Frank Leahy, a championship coach of Notre Dame, once remarked, "Criticism is like money. A player should not worry about receiving it. He should only worry about a lack of it." A player cannot improve if he doesn't know what he's doing incorrectly. And a father/coach will either be too critical and have it fall on deaf ears or not be critical enough and risk hampering the development of his player.
Coach Wade of Football for Youth.com estimates that between 75 and 80 percent of youth coaches get involved in coaching because of their own children. So it seems by that estimate, it would be nearly impossible to avoid such pitfalls, but the effort should be made. There are coaches - most of whom do it for a profession rather than a father-son picnic - that are dedicated equally and serve the community with bias. Those coaches should not only be appreciated by parents and leagues, but promoted accordingly.