I like to retain lots of the original ... brainstorm stuff associated with your mate, especially spouse, kids, significant others...hobbies, &c. &c. Have fun with it. And practice {aloud} lots, so you're not glued to a paper or tablet.

I had a hoot doing custom lyrics to this tune for a friends' 25th anniv.
He's your best mate. Give it your best shot!

keep on pickin'
dennis