The will and directive really is important. I was really glad that my mother had put all that stuff together when she was first diagnosed, and then we sat down and talked really honestly and openly about her wishes. It also meant that I could shove all that in my awful aunt's face when she was trying to bully the nurses into measures I knew my mother wouldn't want. It's hard for people who love someone to make those decisions in an emotional state, so doing it now helps you and them.
Hopefully it's not needed and all goes well, but organizing all that is probably one of the most loving things you can do for the people who care about you.