Really good idea, and so important. This could help relieve much suffering and bring the only thing that is truly healing: acceptance. It could also relieve substantial unnecessary strain on our health care system.
Cool idea! And the reasons you describe for needing something like this are insightful and true. Having these kinds of records can be tremendously meaningful for a family, but getting them can be awkward.
This is a great idea. I actually discussed throwing just such a party with my stepdad while he was progressing toward death from leukemia. He and I conceived it as a "retirement party." However, I echo Ken's comment that this event needs to be designed to happen while the person is still well enough to participate and enjoy it. In my stepdad's case, the idea came to us a little too late for that.