This one (although I usually use it as a birthday song) would work, I think. It's to the tune of Silver Threads Among the Gold.

[Darling/fella/Charlie/Charlene], you are growing ooo-old
Rocks don't get as old as you!
You're not quite as old as God is,
But you're older than primordial stew!

Yes, my [Darling/fella/Charlie/Charlene], you will be, will be...
Older than the rocks and trees
Yes, my [Darling/fella/Charlie/Charlene], you will beeee-eeee
Older than the rocks and trees!

Dave Oesterreich