Do children need to know for whom the bell tolls?

A friend of ours has just discovered he has a serious illness. Once he gets over the shock I think he can face the gravity of all this. I think, or hope, that at some point  my heart won't sink like a stone when I think of him. But the awful part, the thing I can't get my head around is that this has happened to a young, vibrant person with a daughter the same age as my son.

We parents struggle mightily to ensure death or nothing related comes near our children. We will give up our own lives to preserve theirs. Death is something that will come for all of us but we want to put it off as long as possible, more I think, for our children's sake than our own.  As I type these words my son skitters about the kitchen making a get-well card for his grandpa who is hospitalized with pneumonia. Grandpa's wife, my son's Nana, sits distraught 3,000 miles away. To cheer her up my son empties his Halloween stash and requests that I take him to the post office tomorrow so he can mail Nana a snack. 

To my son, sick feels like an aching tummy or a stuffed up nose. He is innocent of the word's wide and horrific bandwidth. I would like to keep it this way (he is only 7) but two of his friends now have seriously ill parents. Time to pick up one of those books I've passed over in the bookstores, the ones advising how to talk with young children about death. My instinct is to go slowly, but I also don't want him struggling for answers alone.