Casey Kasem's children wanted him to die so they could collect on his sizable life insurance policy -- so claims the DJ's widow, Jean Kasem.
Jean tells TMZ ... Kerri Kasem called the funeral home and asked how quickly they could issue a death certificate. Jean thinks it's a money grab --- "Their impatience for Casey to die was obvious when they killed him and now their impatience to collect on the life insurance is even more telling."
Jean also scoffs at the private memorial Casey's children held over the weekend ... telling us, "We have had to once again handle all of their incessant sleaze peddling while preparing the arrangements for a befitting funeral for Casey."
Speaking of which ... it's unclear why Jean hasn't had Casey's body flown down to L.A. for a burial ... more than a week after his death.