C.S.
I don't have any good book recommendations but we've also dealt with this issue.I've found with my daughter - also 4- that at that age they really take cues from you on how to respond to all of this. So we are careful to remain positive and make sure she knows what a great place heaven is. We answer her questions as simply and briefly as possible and then move on to another subject- harping on it will not help. As I said though- your reaction is important- let her know taht you are happy for the dog and great grandpa because they are in such a great place where there is no pain or sadness. Acknoledge the sadness but move past it quickly. I'm sorry for your loss. I'm not sure if they've started but soon will come the questions about your mortality and his own- these are tough as well- again simple short answers and move on.