Here is a very informative video that will be of great benefit to you and your loved ones. The Letter Project provides all the materials you need to leave your family a letter that they will cherish for a lifetime. It will also be therapeutic for you as you share your deepest feelings and thoughts with those you love the most. Here are the links I promised.
The Letter Project website – http://med.stanford.edu/letter.html
If you are currently in good health template – http://dearfamily.dear-doc.appspot.com/html/healthyletter.html
If you have any chronic illness template – http://dearfamily.dear-doc.appspot.com/html/sickletter.html