I am sorry for the loss of your grandfather.
Here is one I would suggest; the Nunc Dimittis
Now, Master, you let your servant go in peace.
You have fulfilled your promise.
My own eyes have seen your salvation,
which you have prepared in the sight of all peoples.
A light to bring the Gentiles from darkness;
the glory of your people Israel.
Glory be to the Father and to the Son and to the Holy Spirit,
as it was in the beginning, is now, and ever shall be,
world without end. Amen
Another suggestion would be to call your parish and ask for an appropriate prayer to say.