It's just an email, not a Jnanpith Award-winning novel. You only need to tell them that the holiday list is attached and to contact HR if anyone has any questions. Also, put a copy of the list on the noticeboard. Job done. Don't overthink these things. Remember the KISS principle. Simple things like this should be a no-brainer even for a fresher in HR. Do you write emails to your friends and family?