Probating an estate is a very long and arduous process. Especially if it there wasn't a Will (Source: Newly an ADM of an estate). It's likely a highly emotional time for the family. Such a document or topic could likely get "lost in the chaos" and be an unnecessary complication. PLUS, inheritors of an estate may not always have the best interests of the deceased in mind. Finally, it can take well up to a year for the family and attorneys to finish resolving an estate. With all of that in mind, it would be wise to wait a year and then contact people until you can find administrator(/executor) and inform them of your wish to help publish the deceased's work.
Considering there is a coauthor, most of the above may not actually be relevant! Simply do as the deceased asked (review draft, provide feedback, etc.) and then relay everything to the coauthor. Then wish them good luck, offer your help, 'sorry for your loss', and that's it! It is between the coauthor and the admin/executor of the estate to decide to publish or not to publish.