I hope this message finds you well, present circumstances excluded. I am a licensed attorney with over a dozen years of criminal law experience. It is a pleasure to assist you guys today.
You guys need to hire a criminal defense attorney in the county in which he is charged that is experienced in dealing with the prosecution and the judge that is assigned the case. This is a situation that could be much worse if he were one year older. Since he is a minor, this will end up being alright in the end.
That said, we need to work to keep this off of his record relative to college applications and the like. Since he is a good kid with no priors and since he was arrested with a group, this is a case that can and should be remanded to the file (meaning he is never convicted if he completes some court ordered parameters - community service, write a paper, etc.).
So, when you meet with an attorney, you need to make sure that you let it be known, the goal is dismissal of the charge altogether, or remand to the file. The website avvo.com is a good place to look for attorneys in the particular jurisdiction that is at issue.
Let me know if you have any other questions. Please also rate my answer positively (THREE OR MORE STARS) so I can receive credit for my work.
Best wishes going forward!