I should probably mention.

Yeah, I forgot to give a general age to Amethyst, Midnight, and Bright. I called them fillies and colt because that is closer to what the age is. If you forsed me though I would have to say
Amethyst-15
Bright-14 or 15
Midnight-16

Teens are still considered kids. Also if I do it that way I can open more story and adventure options in the story.
I am also working on a extra chapter that won't be too long but it involves the future Rainbow Dash and Twilight. It should also clear up a few questions.