Need advice on a possible assault on a minor

Can someone tell me if this is considered assault on a minor in the state of Colorado. Sorry if I am posting in the wrong forum.

My son, age 13, plays football in a local youth league. His team's last game became very heated when a referee called the game early for a questionable reason not related to the following incident with my son. There were comments flying back and forth between some of the parents and the refs. One of the parents involved was his mother. A coach, from the other team, told his mother to leave and made a few other comments to her. At this point my son told the coach to "Shut the f#$k up and leave his mom alone." (Please no lectures on his language. I have already chewed him out for this and he realizes it wasn't the smartest thing to do.) At this point, the coach grabbed my son's arm and started pulling him toward the exit of the field. When my son didn't move the coach started chest butting my son to get him to move. At no time did my son threaten the coach. After the chest butting my son just walked away.

So the question is does this constitute assault on a minor? Can I press charges? One of the problems I have is that the league president is a police officer and given his reputation if I file a complaint in the town the act was committed it will get buried. If I do press charges do I do just file against the coach (his identity is unknown at this time) or can I file a complaint against the league since the coach should be considered their representative. This league also has a history of problems with a disregard for minors safety. This history includes a ref jerking my son to his feet, by his shoulder pads, last year when he was laying on the ground obviously in pain. An issue I discussed in great length with one of the league officers at the time. Can I file a complaint in my home town? Any help would be appreciated. Thanks....