-Elderly folks should have a trusted younger person with Power of Attorney, and Power of Attorney for Healthcare.
-Heirlooms should be listed by description, value and intended recipient (and maybe a second if the intended cannot accept or refuses a bequest).
-Elderly folks with anything more than simple investments should execute a document explaining how such assets are held, valued and a strategy for disbursing them. My father died two years ago and my mother is still dealing with liquidating a complicated investment he had made
- Younger people with children should revisit their choices as to placement of surviving minor children at least yearly
-Life insurance should be reviewed annually to account for changes in family situation
-People of all ages should be encouraged to have disability and at least a million-dollar liability umbrella policy
As others have said here, personal information that might not be known to surviving heirs (family history, especially about health histories- cancer, heart, liver problems- of immediate relatives can be invaluable).
I would also suggest as your children get older that you talk to them about who they want the guardian to be.
A sixteen year old will not stay where they don't want to be.