Not breathalyzed, not drinking, yet getting into trouble. What to do?

Just be honest and explain your situation. Don't get angry or defensive, because they will see it as you trying to get out of this. Also it's important to mention you were not breathalyzed, they are supposed to do that. Also ask the 17 and 18 year olds if they will vouch for you. Explain to your parents what happened. You haven't had any other offenses, so you should be okay.