Ideas to include
The grandparent chapter
The grandchildren's names, what they call them, the Sunday ritual that has already become tradition. A whole new role, usually two years old, and worth a verse of its own.
Still going
The garden, the choir, the half marathon, the trip they have booked. Tell us what is next in their diary so the song faces forward instead of only looking back.
The thank you nobody says out loud
What they carried for the family for thirty years without mentioning it. Give us one concrete example and the song can say it plainly, without a speech.