A lot of very rich people are also very cheap.
As for the "key" idea, yeah, we are looking to get a safety deposit box, with documents on where stuff is, safe combos, etc. So, if we go, our kids can actually locate everything. (not that they deserve it, lol)...
But, we are also looking to do all kinds of pre-planned and pre-paid funeral stuff, so that when the time comes, they don't have to lift a finger. (not so much out of concern, but more because there's simply a) no way they could pay for it, and b) no way they'd be able to follow any of our wishes).