I hope your crow friends follow him and shit on his car until he’s thoroughly spooked. Also, I’d probably get out a hose and wash away all signs. But you shouldn’t have to.
If someone asked me if they could scatter the ashes of a someone who grew up in my house, I'd be like, "sure, do you want to plant something for them too?"
If it were that and also that specific, I probably would too. But if someone asked if they could spread the ashes of their buddy who murdered his girlfriend in my house and always wanted to be reunited with her for eternity? Well, that would be creepy.