How will future earnings be distributed? Will they go to one person or set up in a trust?
Who will make decisions regarding the rights to the work? Just because a book is published doesn't mean decisions regarding its rights are finished. There are times when the publisher will ask for revisions (and in this case want to hire someone to do revisions), they might want to change or update the cover or, if its a series, continue the series. Who will be your go-to person for these decisions?
What will happen to other works? Will you allow "found" manuscripts to be published? What if you are in the middle of a contract? Are you okay if the family opts to hire an outsider to see the contract through?Once you've established the legal portion concerning your books, don't overlook the day-to-day business of your publishing career. My suggestion is put together a file and let everyone in your family know where it is and what it's labeled. Maybe label it with the name of your children, spouse, niece or nephew so they won't need to remember what it's called, but it will easily stand out to them when they're searching for it.
In this file you should include a list of all your publications, earned or unearned. I've had situations where a book never earned out, until it did, at that point sending checks became difficult since no one kept me updated with contact information.
Include who handles the statements or sends checks for those books. If they are self-pubbed you'll need to include detailed information for each account from which you receive money. I would suggest including all passwords and how payments and statements are distributed.
If you have an agent you'll need to include the agent's name and her contact information so the family can get in touch about statements and earnings.
I don't think preparing to make your family's life easier is that difficult, but I do suggest it be done. Until I hear from next of kin and am given strict instructions on how to move forward I will continue to send checks in the name of the author. I'm unsure how long that's going to work for the family or how it will play out during tax time.