Finished Basic trng in Canada in June and it lasted 14 weeks. He needs to be able to do at least 19 push ups. Two tall guys in my platoon couldn't do them as their frame was so long.
Then there is the 19 hr work days and PT twice a day along with ruck sack marches and lots of verbal abuse and group punishment for the individuals failings that are a part of training that a lot of recruits find difficult to tolerate.
I am sure your son will do fine. It is only a matter of remembering that all one's buddies are going through the same thing. Knowing that really helps. That is where the bonding begins.
I wish him the best of luck in his endeavours.