Now that we are agreed that, at least in the UK, allowing passengers to manipulate the controls is legal, does anyone allow them to use the radio?
My understanding is that this would be frowned upon as they are not under training and are therefore not exempt from holding a FRTOL.
Pretty sure that would not be legal, at least in UK. An untrained person could cause all sorts of problems if the transmit on a busy frequency.
The rules surrounding use of aeronautical radio are pretty strict. When the BA engineers got electrical power onto our Concorde (G-BOAC) at Manchester and it all came to life, we had the radios tuned to the Tower and switched through the cockpit speakers. I was very tempted to plug in my headset and call up on the Delivery frequency "Manchester Delivery, Speedbird Concorde Alpha Charlie radio check".
That would have been a bit of fun, but of course illegal not least because AC's radio fit is no longer a licenced installation. So I didn't!