I am so sorry for your loss hun. I can't even imagine what you're going through right now.
It reminds me how fortunate I am to still have my dad here, even though he has had two major heart operations and will be on medication for the rest of his life. I dread to think what my life will be like without him.
Agreed with Sam's mum there. It's exactly what your Dad would have wanted, who wouldn't want that?
Take each day as it comes and try not to dwell on the future. Your son might not see his Grandfather again but you will tell him of all the wonderful and cherished memories of him. And at least you have that photo, I'd advise you to get several copies of it as one is never enough and too precious to lose if you ever did.
I never met my Grandmother because she died of cervical cancer and breast cancer when my mum was just 13. But my mum has shared some wonderful memories of her and only wish I could have met her. We've also got her photo up in the living room, one of very few photo's.
Take care of yourself and if anything, try to celebrate your fathers life. Sitting around with family and bringing up memories, laughing, smiling and occasionally crying is really helpful
My thoughts go out to you and your family xxx