The great secret that all old people share is that you really haven't changed in seventy or eighty years. Your body changes, but you don't change at all. And that, of course, causes great confusion.
The deep, personal material of the latter half of your life is your children. You can write about your parents when they're gone, but your children are still going to be here, and you're going to want them to come and visit you in the nursing home.