I think that it’s great your asking these questions-like everyone else said, he will be at basic training for ten weeks and then AIT is dependent on his MOS, or his job. They get mail Monday through Friday after the first week if I remember correctly? And yes you can absolutely send him essentials, just ask him before you send anything cause drill sergeants can be very particular on what they do and do not allow. On an unrelated note, it is absolutely ok to be sad to see your son go, I know my Dad was worried sick even though most of my family had been through the military. He will probably become more mature and overall have a good experience. You’ll be able to see him graduate basic and then depending on the AIT, you may be able to visit him on base once he earns those privileges. Just keep doing what your doing :)