What should he plea? malicious destruction of property

What is the name of your state? Michigan
My son received a letter in the mail, stating there was a warrant out for his arrest for malicious destruction of property. He went and turned himself in and they gave him a court date, tomorrow.
He and his friends knocked down several signs in a residential construction zone. It is on camera.
Tomorrow is the arraignment. We have never had any legal problems before.
I understand that they will read him the charges, his rights and will ask for a plea. What should we do??????
Every job applications asks have you every been charged with a crime. Is his life ruined forever??
We don't have the money for an attorney.
Does anyone talk to you before hand or does this all happen in the court room?
He is 19 and a little slow and very shy.

He can enter a plea of not guilty and request a public defender.
He'll probably be scheduled to appear again in thirty days and the public defender will tell him what his options are at that time. (Unless they contact him before hand, but I wouldn't count on it)
If he really is on film, the public defender can get a copy of the video to review in the discovery process.
If there actually is video of him, how did the people who reviewed it know it was your son?
Is he well known by the police or the folks who reside in this neighborhood?
Sounds to me like maybe one of his partners in crime gave up the name of everyone who was there.

Most job applications ask if you have been convicted of any crimes and usually a felony.