Aeroflot Flight 593 ended in a diaster - see link below (well worth watching). Reason being a kid was at the controls messing up the autopilot.
https://www.youtube.com/watch?v=k4y3dcqx10s
In my opinion there is no need to start a discussion here. A cockpit is not a playground and there should be only authorized personal in the cockpit and certainly only qualified and trained pilots at the controls! For any other purpose of "entertainment" go mess around with a simulator!