My question involves juvenile law in the State of: NJ

My son was at the Jersey shore for senior week and the police raided the house he was in the first night he was there. There was alcohol at the house and my son being 17 was taken to the station and I had to pick him up. First offense, under 18, has to do an online counseling course for alcohol and drug abuse. Now I just found out that while at the house, someone gave my son pot to hold. When the cops came in he threw it behind the sofa, not wanting to be caught with it obviously. A few kids are now saying they saw him throw it and the cops found it. They are all 18. One of the boys wants my son to go to court with him and confess that it was his because he is being fined (but his court date isn't until later in July). Not sure on his charges yet - waiting on this kid's mom to call me.
My son is a good kid that has never been in trouble before and was a straight a student. What do I have to do as his mother? Should he confess? Is he covered by the counseling program? I don't know what to do.

added info - there were approx. 20 boys in the house and none of them admitted it was theirs. Can the police pick one and charge them or charge all of them with the same offense? How can this boy say that he is being charged with possession and has to pay a fine of $2800?

I am not trying to excuse what my son did but I do wonder if this kid is being a jerk and trying to get money from my son.