G., I am sorry for your loss. I am very close to my step-dad and hate the word "step"-I call him dad. I don't think books for your Mom is going to help her at this point. She is in shock, she might be numb, and if you give her a book at this point, she may not remember reading it. She just needs your support, phone calls, seeing her (if she lives close by), seeing the grandkids. She will want people around her.
She will need your help making arrangements and getting things organized. Don't worry about the house right now, just take one day at a time. Don't suggest her moving out of the house, she will eventually make these decisions on her own without being pressured. Now is not the time.
My brother was killed in a car accident 3 years ago, he was 24 years old. We talk about the first 2 weeks of that, and she told me it helped having people around her. She told me she doesn't really remember much else, just people. My dad told me the same thing. My mom used to shy away from people who suddenly had a family member (spouse, child, parent) die. She is now one of the first people at thier door, with food and a shoulder to cry on. She also tries to help them figure out funeral arrangements and makes suggestions, as a friend.
As for Children's Books, I know Maria Shriver wrote a book about loved ones that have died and where do they go. It's called "Whats Heaven". She wrote it after her Grandmother Rose Kennedy died and her children were questioning what was happening. I looked on Amazon.com for the book and saw several others with the same topic.
I am sorry for your loss, and my prayers go out to you and your family at this time.
H.