Not to be too silly about it, but these are tourist flights that are going to have people on board expecting to go on a nice fun flight. Mostly that happens, but sometimes not.
Pax brief, safety cards, that's about it, but perhaps to put it into perspective, it's no different to getting into a bus or taxi, or even on a theme park ride - things may happen. What are you going to do, mandate comprehensive HUET training in five languages for all pax on any scenic flight anywhere over water? Terribly sad for these individuals and their families, but you can't wrap the whole world up in cotton wool.