Elisa, their behavior as children has no bearing whatsoever on how or what they'll be as adults. When time to choose a new gen the game randomly generates everything about them; personality, age, job. The only thing they maintain from their childhood is their name and likes/dislikes, as well as their place on the family tree.

I generally just choose the peep I like most when the time to choose comes up and rarely make that choice before that time.