How to Start the Conversation
I would suggest two good books, though there are many more, I'm sure. "Creating the Good Will," by attorney Elizabeth Arnold, emphasizes legacy. Arnold has helped guide many families through the process of end-of-life legal work and she sees that there is much more than mere objects to leave behind. Some people, helped by this excellent book, may find that they want to make their values and wishes for their family's future a part of their end-of-life paperwork. The book is worth reading if you are having any difficulty in deciding how to broach the end-of-life talk, no matter what your age or state of health.
The other book I recommend is "The Parent Care Conversation," by Dan Taylor. This book is also about legacy, but has more information about planning how the parent wants to be cared for. It covers legal work as well. Both books offer insight and are worthwhile reading as each has its own strength.