Couldnt agree more with whats been said already. A good ground briefing on what to expect at various stages is really worth it e.g stall warner on take off if its a bumpy grass runway, current weather (if it looks like its going to be a bit choppy) and actions to take if the fan stops after take off.
Make sure you take plenty of sick bags! I took a mate up who said he could read a book as a passenger in a moving car and has never experienced motion sickness in his life. We did a couple of steep turns over his house and he soon turned white and went very quiet... . .This can be brought on from staring at the instruments too much. Get them to look outside and help with the lookout.
OTB <img src="cool.gif" border="0">