Swoop -
My own words fail me. I've lost most of my family so I can say I know what you're going through, but I don't only you do.
His life is truly to be celebrated, speak of him - as you do - fondly and with a huge sense of pride in his accomplishments, and joy at where he is now.
As the song says:
Looking down he said, some day you'll understand
we're the lucky ones to be have a reason to be sad.
He said our tears are a reflection of the good times we've had
If we'd never known love, we'd have no reason to be sad
The good times were so good, and that's why it hurts so bad,
we are the lucky ones, lucky to be sad.
God bless your grandfather, and may He bring peace to you and your family with the knowledge that God has blessed you all with such a wonderful reason to be sad.