As I recall, I would meet the trial lesson student and have a quick chat with them , and family if present, at first in the reception area or upstairs in the lounge. You can quickly see which category they fall into. Then I would find out where they came from and show them my chart, point out where the airport was, and where their home was and recommend we fly over it, time permitting.
Then out to the aircraft - take the family for photos - let the young child sit in the plane that daddy was going to fly in if he wanted - quick walk around pointing out the control surfaces check the oil and tyres then get in.
Explain the six flight instruments in front of him and the engine controls. Show how the control column moved the ailerons and elevator then safety briefing.
Then patter through to to top of climb, trim the plane and show the effects of the controls - but not paricularly secondary or speed effects and hand over to them.
Let them do as much as they wnat or are able until over there house. Do a few turn over it, let them fly back and take over when appropriate - top of descent or short finals depending on ability and weather.
I don't think giving a formal lecture in a briefing room is a good idea. For most it would be intimidating and over the top and I would never have had time - 45min slot for a 30min flight.