Awww! What a great idea!
I could probably come up with hundreds of songs given the time.

I'm a bit of a music nerd. I have quite a catalogue. But I'll try to keep it short (sort of

)
Peter Bradley Adams
For You
Little Stranger (Not sure how well this one would work for your video but it's our personal favorite. Rick sings it to Ellie as a lullaby and it makes me cry every time.)
Family Name
Carole King -
Child of Mine
Rob Thomas -
Little Wonders
Steven Curtis Chapman -
When Love Takes You In
and of course you can't go wrong with Sister Sledge - We Are Family
Have fun making the video.