Ideas to include
The origin story
How they met, the wedding nobody could afford, the first place they lived. Fifty years on, these details have become family legend, and the family loves hearing them.
Everyone in the room
The children, the grandchildren, the great grandchildren. Name them and the song shows what fifty years actually built, which is the whole point of the day.
Fifty years of small things
The chair nobody else sits in, the phrase one of them always says. Half a century of tiny rituals the family could recite, and that no card ever mentions.