On the FAA side of the pond there is something called the 'FAA Passenger Brief' and it is, IIRC, a requirement before taking off with pax. Note that it's not called anything nearly as grandiose as 'Captain's Brief'. What this does (and I do it every time I fly with pax, especially those who aren't around small a/c a lot) is to explain emergency procedures, where the lifevests are (yes, really!) ask not to interfere with flight controls, communications between pax and/or myself and usually also ask them not to jabber away while ATC is talking (on some of the a/c I fly I can isolate the pax intercom, on some I can't). I usually also tell them the initial departure route, pointing it out on the chart and warn of any expected turbulence.