As I understand your question, the concern is that kaddish either cannot be recited or will be delayed because of the donation of the body for science.
From a Reform point of view the donation of one's body for scientific study “is most certainly an instance of pikuach nefesh (saving a life)." In contrast to those who might consider the donation of a body for medical education as something less than pikuach hanefesh, we hold that "if autopsy is an essential feature of medical education, it makes little sense to delare that we aprove of the saving of a life but not of the means by which medical professionals are trained to accomplish that goal... Our position presumes that the remains will be treated with the respect due to the human body (kevod hamet).” [Jewish Living: A Guide to Contemporary Reform Practice, Mark Washofsky, UAHC Press, 2001,, pg 189]
Based on this understanding there would be no reason to assume that the recitation of kaddish would be affected. Beginning with the time of death, or following a memorial service, the mourners would recite kaddish just as they would following a standard burial.