What is the big deal?
Having the Captain's son in the co-pilots seat is no worse than having it empty!
Hell, back in pre PC days the cockpit door was open and the captain made sure the prettiest passenger with the shortest skirt jumped into the P2 seat preferably with the co-pilot still there. Well I guess that was when flying was fun and there was no fear of being "reported"
This incident is no way like the russian captain who allowed his son to take his seat!