Kudos to you VTGirl for thinking about this, I wish everyone did.
I was on the receiving end of a tragic dog inheritance situation, and it was a stressful, expensive, mess. Someone very close to me died suddenly, young. He owned two intact, purebred dogs that he loved very much. One was sweet and social, and the family nearly tore itself apart fighting over who "got to keep" her. Nasty arguments, giant mess, some of them are still holding grudges because they didn't "get" her. The second dog was intense, drivey, disliked children, and was strictly a one-person dog. When her one-person died, she decided to tear a piece out of the other dog's face, destroy a couch and tear up the floor. Somehow, that dog knew something was terribly wrong and her one-and-only person was dead. No one wanted anything to do with her. She ended up with me.
We had no idea who the breeder was, the paperwork never surfaced, all his girlfriend knew was "He talked to a breeder for months, and then he left for three days to go pick up the puppy". Not very helpful. No chip, no tattoo. Thankfully the vet's office was willing to turn over the medical records to me with minimal documentation. Even so, it cost me a ton of money and grief, damage to my house, and I had to drop out of agility with my own dog so that I had the time to get my "inherited" dog through obedience classes and deal with her reactivity.
That particular dog's story has a happy ending, she's well loved now in her forever home, and I see her often. Stable, happy, snugglebug. But the process was a nightmare, and I wouldn't wish it on anyone.
I have a written document that dictates what happens to my dogs, should my husband and I die suddenly, and I would strongly recommend that everyone have something similar. Breeder contact info, training history, registration info, trainer contact info, and a written letter authorizing your vet to release all of their history to a named person. One of my dogs would go to my father, who loves her dearly. The other would go "home" to her breeder. Everyone involved is aware of the arrangements.
I wish everyone thought as far in advance as you are. Though hopefully the need never, ever, surfaces.