Children of the Night is the general term for all vampires across the world, since most vampires in their nascence are induced to sleep every day only to rise every night and hunt for fresh blood. Although the phrase is used universally, mainly by Benji Mahmoud, who broadcasts his radio program to every Child of the Night, it is specifically directed at those vampires too young to endure any sunlight lest they immolate or are severely burned.
This idiom appears in Prince Lestat (2014) and Prince Lestat and the Realms of Atlantis (2016). For more perspectives on the Children of the Night, read the Alphabettery entries Benji Mahmoud and The Voice.