End of Life Talk. There are many ways to approach this issue. Comfortable setting for the parents. Using yourself as an example is a great way to break the ice. "you know mom and dad, i just signed these documents about what i want at the end of life. Have you done that yet?" this is just one strategy that will help for resusitation concerns. Donor concerns can also be handled in this manner.
Another approach. Tell your parents that you want to be prepared if anything happened to them medically that left them unable to tell you their wishes--so that they do not think you are expecting them to die! tell them that it will help you speak for them more clearly and help you be more confident when you speak to their doctors.