Adam and Ghosts

Adam (my 6 years old) is seeing ghosts. Sometimes they are blurry and sometimes he names them. My Dad passes away 3 months ago and my Nana passed away 3 years ago. (My kids were very close to my Nana and loved my Dad)He says he sees their ghosts. And a ghost of himself. I'm not sure what to make of that one. He has also decided he wants to be a baby like Sara, so he can sleep with me. ( Sara is 14 lbs. Adam is 65 lbs. and very wiggly)Anyway, we have tried many different methods to help him sleep at night, ( o' he has been crying when nighttime comes, he only likes daytime). We put the regular lightbulb back in his room so the dimmer switch will work, we pray, we hung a picture of Jesus in his room, we have talked until we are blue in the face about people that are in heaven are watching over him and are not scary. ( We are not a religious family but we believe in heaven. ) We are exhausted and really hope this 'phase' passes soon. I am assuming this is grieving but I don't know. He is a wonderfully bright child and soooo smart. He is also sensitive and a softy. I hope will be able to move past this soon and sleep better, and not be scared of nighttime.