I would go with Yours (as in the new baby is all yours to love and play with)
Yawn also works for needing more sleep which ALL new parents can identify with.
Yessir, that's my baby! from the old song
You're all I need (from a song also)
You are my sunshine
You light up my life
You are the wind beneath my wings
You're the one that I wanted (play on another song)
YEAH! for congratulations on the new baby
Hope this inspires SOMETHING.
Carol O.