I'd like to be able to play a kid character

[lololink]

Technically, we should be going by 20 as that's the age of majority in Japan...although you are still correct.

Firion - 18
Luneth - 14
Cecil - 20
Bartz - 20
Terra - 18
Cloud - 21
Squall - 17
Zidane - 16
Tidus - 17
Vaan - 17
Lightning - 21

Only 4 of the main protaganists across the released mainstream games are off-age in Japan. And then you have Luneth...14, really?

And then you have Lightning who finishes her story aged 521 years old...

Luneth is very old actually, since they were stuck in the limit between the flying island and the land flooded under the darkness that stopped time.

[Rustyhagun]

Elezen and Hyur have a "youthful face" choice, for your character face type. It makes you look like your in your early-mid teens. Choose that face and the shortest height, And your good to go.

There is even a 'freckles' choice, in the tattoo section of character creation, to add to the affect.

Don't just pick lallafel.