The basic principle that an individual is free to make personal choices applies to children as well. However, children are much more in need of guidance and training and support than grown-ups normally are. There will normally be grown-ups around to ensure that children learn how to make choices that work in their lives and that they learn how to relate to others and to society.
The common notion in HoloWorld is that it is much more desirable to help children be responsible citizens than it would be to make them obedient slaves. Thus, the understanding, caring and self-motivation of children is what is cultivated, rather than their willingness to follow orders blindly.
Children are not owned by their families. Their families are their primary caretakers, except for in communities that choose to rear children collectively. However, in either case, a child has the choice on where to belong as soon as he or she is able to make it.
A child has the right to leave a family if they are able to make an informed decision on that, and if there is another family or community that is willing to take responsibility for the child.
There is no agency that has any right to take children away from their families when the children don't want to be taken away. It is the exclusive decision of the respective families AND the children whether their current arrangement works or not.
Children will gradually get more and more responsible roles in their communities as their bodies and minds develop. There are no artificial rules for when a child is legally responsible. He or she is responsible when he or she is responsible.
It can be very damaging for a person's development to be treated as a child until the age of 21, when from nature's hand one is fully grown years before that. HoloWorld has no such pre-written legal distinctions.
Indeed children can make very valuable contributions to society with their fresh perspectives and playful attitudes. This is to be supported and treasured.