Our DD is another in the 'no sheltering' boat. We figured early on that she seemed to just know a ton of stuff she shouldn't and that the best bet was to just be upfront. I remember reassuring her (this would have been before her third birthday) that while yes, all living things die, humans tend to last a really long time and none of us were planning on dying any time soon. But she wasn't hugely upset, more mildly concerned. When she was 7, she chose to be in the room when we had our dog euthanized and it was a very positive experience for the whole family in terms of dealing with sorrow and mourning at losing our good friend.
She's sensitive about so many other things (perfectionism, criticism, change, finding meaning) that I'm glad she's not also sensitive to these other adult topics.
