Your son needs to understand his rights. Whether he is guilty of this offense of not, no defendant walks into his arraignment and just pleads guilty.
By both custom and right, all defendants plead not guilty
This is because in this country our law deems you innocent until proven guilty beyond a reasonable doubt. And we also have a 5th Amendment right that says we never have to incriminate ourselves in court
A plea of not guilty is the only plea that keeps all of a defendant's rights open so that he can fight his case or negotiate a disposition with the prosecutor. Any other plea closes doors and results in a criminal conviction which can get in his way for the rest of his life.
After you plead not guilty, you can always change your mind and plead guilty once you've worked out the deal you want to get. BUT if you plead guilty in the first place, you are locked into the consequences that the court gives you, and you can almost never change your mind if you don't like the news.
So he should not admit his guilt and take a plea until he knows in advance exactly what the prosecutor and judge will want him to have as a sentence
If this is his first offense, since these charges are all non-violent
misdmeanors, he should be eligible for a deferred disposition of some sort. That's a special form of community supervision/probation which consists of fines, community service, classes or counseling, as well as supervision. At the end of the supervisory period, if he has completed all of his requirements successfully, the charges against him will be dismissed, so that he will end up with no criminal conviction.
Short of an outright dismissal -- which usually is not in the cards and doesn't seem like it would be here either -- it's the best possible disposition he could get because he'll have no conviction on his record.
Obtaining this is not an 'automatic." Even though he's eligible, the prosecution has discretion as to who they wish to offer it to. It all depends upon the facts and circumstances of a particular case and may have to be negotiated for him. But it would be a very reasonable disposition for an offense like this.
He also ought to have a lawyer if he can afford one, as some DAs will not negotiate with unrepresented defendants. If he can afford one, he should have him with him at his arraignment. If he is indigent and cannot afford a lawyer, after he pleads Not Guilty, he can tell the judge he cannot afford a lawyer and ask the court to appoint him a public defender. The PD will be able to negotiate a disposition for him, and it will usually be a more favorable one than anything he can get for himself.
Good luck to your son.