May God bless you with wisdom and words.
2 Corinthians 4:16-18
New International Version
16 Therefore we do not lose heart. Though outwardly we are wasting away, yet inwardly we are being renewed day by day. 17 For our light and momentary troubles are achieving for us an eternal glory that far outweighs them all. 18 So we fix our eyes not on what is seen, but on what is unseen, since what is seen is temporary, but what is unseen is eternal.
I spoke about salvation at my mother's funeral. I have also done other funeral services. The heart of the deceased is often to see those he/she left behind saved and coming to the kingdom. My advice is to honor your father's wishes, but don't expect any sigificant response. The word of salvation is often like a crop, first a seed must be planted and then a growing season comes before a harvest. You are tending the field the master (your father ) left behind, do it honor.
Yet death is a great reckoning to many as they try to understand what life is about. Solomon said it best, it's useless without God, we are here for a moment and gone. The true life lies within the Kingdom of God and is eternal. Your father knew this and because of the great Love the Lord had put in his heart he cared, even in death, about others. Tell them how much he loved them.
Sorry for the long post. I started out with a simple sentence promising to pray and I just kept typing.