Question 30: What is the ruling on those who embrace Islaam while their parents are still polytheists who worship idols until they die? Is it permissible for their Muslim son to participate in washing and burying them? What is the ruling if the son participates in washing and burying them and other ceremonies of the non-Muslims? What should a Muslim son do after these acts?
Answer: As a general rule, when a Kaafir (Disbeliever) dies, their relatives should hide their corpse in a hole so that people will not be harmed by them… read more here.