Hummmm If I had to pick I would go Atticus, are you naming him after Atticus Fitch the writer? If so, that's nice

Have you thought about Jasper??

P.S If you do decide to go with Caspar I wouldn't worry about the "friendly ghost" call. Kids these days don't really know Caspar the TV Character its more of a 80's / 90's thing I would have thought

Good luck choosing!