Stepmom, your ss will be considered an adult at 18. You will not be privey to anything your ss doesn't want you to know. They will not talk to you unless ss gives them permission.
Your husband can apply to be a representative payee. They will then include you as part of the team.
I keep telling them that difficult child is clueless but they won't talk to me unless difficult child is on the extention to give verbal permission.
All this means is that I am pretty sure your son should be there. Call the office and ask.