We have both carried donor cards for many years. Our sons have been aware of this and have had no objection to any useful bits being passed on.
However, now that we are both approaching 70, me almost, my wife not far behind, we are now taking a different course.
Given that we are both probably not containing any useful recyclable parts we are going to end up here:-
http://www.kcl.ac.uk/biohealth/study/departments/anatomy/lao/donation/index.aspx
Terry