Isn't the reason we are REQUIRED (by NFHS) to be on the field 30 minutes befor the game begins designed to prevent any ridiculous foolishness from happening, upto and including admisistering UNC penalties, including disqualification? That control and responsibility would include the Coin Flip.
Competitive taunting, and any sort of negative interaction (pushing & shoving) before a game begins, if left unchecked, is ONLY going to get worse after the game begins. Shut it down HARD early, or accept dealing with it, likely A LOT WORSE, later on.