With the death of the mother, the divorce proceedings have abated and it is no longer relevant. As the spouse of the deceased employee, the father is entitled for family pension. He also entitled for a share in the retirement benefits.
While disbursing those benefits, the Head of the Office, is required to act in accordance with the nominations, as in the service records.
The property bequeathed has already vested with the beneficiaries. Take further steps in accordance with law and procedure. Empty threats are better ignored.
The children can seek maintained from the father, if otherwise eligible.