Almost Ready for Flight

I'm polishing, polishing the details.  My wife is finalizing the cover illustration.  I'm giving the text one last look.  One last item I'm strugging with regards copyright.  The last stanza includes lyrics to an old song.  I'm not sure if I have permission to use them.  Can anyone help me with the legal issues?  Eternal gratitude and a Smashbooks coupon are at stake.