Do the grandchildren whose father died before their grandmother inherit from her, and is it permissible for them to donate their share to hospitals with the intention of reward for their parents?

If the father passed away, and then his mother (the grandmother) passed away, the grandchildren have no share in the grandmother's inheritance due to the presence of a direct son of hers. For the son of the son does not inherit when there is a son present; he is blocked by him, a complete deprivation.

If the grandmother left no heirs except her sons and daughters, then her inheritance is divided among them, with the male receiving the share of two females, and the sons and daughters of the son receive nothing because they are blocked.