Actually, if he has commissioned and has those papers as well, they should let him in. I had no problem getting uniforms with just my commissioning papers at Luke AFB. Also, when you sign in at the visitor office, you will need car registration and proof of insurance I think.
It is really hard to get the ID before COT. You don't need the id for the POA paperwork. Jag can help with the POA stuff. But I think if your name is on his orders, you will have no problems with household pickup. I got my son's ID when he joined me here.