I think it's unfair to a passenger imply to them that there's nothing that
can go wrong. Even if you are dealing with someone nervous about flying,
telling them that there's no risk is just plain lying and in the long run,
I
don't think it's the right choice.

I've found it best to modify the safety / pre-flight briefing depending on
the passengers. For example - if I have a fellow pilot (or trainee) in the
front right-hand seat, I'll review such procedures as actions I'll be taking
in the event of an engine failure in a twin at various stages - but I won't
for non-pilot folks.

For nervous passengers I've found it best to keep it too the basics
(location of first aid kit + fire extinguisher and how to get out) -
unfortunately if you load them up too much you 'over teach' and retention
goes right down to the point where they can't remember anything, let alone
everything.