More historical context: kids are REALLY ABLE from a young age, especially in a pre-Industrial or agrarian setting. 5 year olds head into the fields with the cows for the day. 7 year olds start apprenticeship to learn a trade. 13 year olds are often seen as adults and can fight in a war or run a school or get married or rule countries (sometimes even with some degree of competence!)

This thing where we think people under 20 are basically incapable of doing much of anything is some serious post-twentieth century and industrialized nation business. Go to Guatemala or Ethiopia today and you will see kids with a great deal of agency and responsibility that we just categorically don’t give kids in much of the US. Some of this is in direct reaction to factory and mine work in the late 19th century and social reformers who wanted kids to be kids, not young adults.

In your typical 500-1700 CE type fantasy settings, every person who can walk has a role to play in helping the family and community thrive, even if it’s just “rock the baby’s cradle” or “gather up wood chips for the fire so we can cook food”. Don’t just fill your world with kids, recognize they have stuff they are doing that contributes and matters; this is part of why kids are not just expendable – their existence counts.