Social Development Question

My Mother died when my son was eight months old and he does not have any memories of this. My wife and I have answered any questions about the death to our son with the best of our ability and without elaborating on anything. Our answers have been literal i.e, grandma is in the cemetery, or grandma is up in heaven because she died; and I think our son is fine with our answers.

Lately my father (widower), whom I do not believe has come to terms with his wife's death, has been taking our son to the grave site to visit. We do not have a problem with the visits and will be taking our son to the cemetery ourselves soon, but our son recently brought us a picture depicting what he describes as "Grandma's grave, papa(grandpa), and me(our son)."

In this picture papa and our son are crying next to the grave. My father has taken our son to the cemetery quite often and we are now speculating on how often this situation depicted in the drawing is happening, as well as how healthy this will be for our son. My wife and I realize that we should be honest about death but not too descriptive right away, but wonder if this situation may have future consequences that negatively impact our child's development.