They were chit-chatting with the uncle of the boy who was a passenger and was standing behind both pilots. I believe the Capt.'s daughter was there too. She sat first, put the hands on the yoke and her dad (Capt.) said to turn soft the aircraft to one side. She did it with minor pressure as the Capt. changed a couple of degrees in the heading selector of the auto pilot system, so it would look like if the daughter physically turned the plane.
Then the son's turn came and the dad did the same thing. By this point the FO was turned backwards talking to the uncle standing behind, the daughter was around, the Capt. was also talking with them and there were suddenly some seconds were the kid was the only one with his hands and his attention towards the aircraft. He tried to turn the yoke but it was locked due to the autopilot being on and was hard to move. As kids are, he tried harder and by this he disconnected the autopilot. I think the aircraft didn't have an audible signal for an autopilot off prompt, I believe there was only a light signal which to the rest, obviously went unnoticed. All this is based on what I've read, I'm not expert in the autopilot system in question.
It was during the night so it was dark, and the aircraft begun to enter slowly into a spiral dive. It is interesting to note why is it that the pilots, after the kid told them something was wrong, only paid attention to discrepancies in the their navigation instruments but not in their flight instruments. I would think one of the first things to check is if the AP is on and if it is or is not then see if the aircraft is in a proper attitude plus altitude, speed, and heading.
As far as I personally agree to maybe take your son to the cockpit just as an observer and behind you when flying airliners and to only touch the controls if we were flying a small Cessna where I can see everything he does, this accident shows how pilots get easily relaxed and can get easily distracted. As a pilot I think you gotta be a bit paranoid; it helps you think in what things could happen if A, B or C. And if it really happens you might find yourself a bit more prepared and anticipate problems. These Aeroflot pilots clearly didn't foresee this.
DU