That is so sweet!
My daughters sing this to their biological father and to their heart father:

Oh my daddy has a first name
It's D-A-D-D-Y
My daddy has a second name
It's D-A-D-D-Y
Oh I love to hug him every day
And when I kiss him I will say
Daddy Daddy I love you
I L-O-V-E Y-O-U