This is certainly a problem, and applies of course to other collections than just books; I collect trains as well.
Let the family pick them over first, certainly, or bequeath specific items where they will be appreciated. Sell the better items on Ebay, if there is some-one prepared to do the work, and who has an idea of what is worth what.
Donate to charity sounds good, but many have no idea of value, and I've seen books sent off for pulping if they don't sell quickly; Oxfam in UK does have a better grasp of book values with specific bookshops and will collect large collections.
Public libraries seem to be in terminal decline, and most councils have no interest in extending their space-consuming back collections. A college or training scheme with a cuisine bent might be an idea, but in the end I think we have to do something ourselves before we pop off, and not leave it to others.
RayS