Japanese name for the Scions?

[Enkidoh]

I would argue that it's more to do with the English version's love of flowery language than anything.

"Scion" is a term used to refer to a descendant or inheritor of something (e.g. scion of the royal family); the Scions of the Seventh Dawn are those who inherited the late Louisoix's mission and carry on his legacy.

And more than that, they also inherited the legacy of Minfilia's earlier pre-Calamity organization the Path of the Twelve, which was to research the mysteries of the Echo and to use it for the betterment of Eorzea, which was amalgamated with Lousioix's group the Circle of Knowing after most of their members were lost on the plains of Carteneau. So the term does make sense (those in the Path of the Twelve incidentally were called 'Walkers', which isn't quite as important sounding as 'Scion' is).