Both my kids attend Sunday School at my parents' church. DS5.5 is waaaaaaaaaaaaaaaaaaaaaaaaay into religion, acceptance and questioning it. He has like 3 Bibles that he looks at and reads religiously (ah, sorry). His acceptance of God and Jesus (my parents and kids are Christian) is truly amazing.
He has never really said that he's seen someone who has passed, but he has an older half brother that passed away when he was 6 weeks old (DH's son), and DS always talks about him.
DD4(in 10 days) doesn't see ghosts or what have you, but she has MAJOR issues with the things in her room "talking" to her at night. So either it's more than her imagination or she's schizo.
I tend to think the former. ha.
Now I will say that I have noticed that ND kids at younger ages also easily accept the spiritual world, religion, etc... I think that while GT might go "deeper" into it, young kids have extremely open/non-cluttered minds to accept things that may or may not be questioned by adults (i.e., religion, ghosts, etc).