Would you really force your children to trek all the way to Skyhold? Knowing how perilous it was to get there? Also what you see of Haven is obviously not the domesticated part, as you only see but what 5 or 6 buildings, of which all are some kind of business or allied quarters for the inquisition, so yeah you probably aren't going to see children running around a budding young army base.
Also you do see one child much later into the game who plays a minor story role.
Also in The Hinterlands while their bodies weren't something i paid close attention to, at least 3 npc were implied to be the child of another npc.
There is the boy who claimed he had the "dreams again" in regard to awakening to his mage power.
I don't think children should be a priority in terms of showing off what DA has to offer, the focus of the game is supposed to be the inquisition itself, and i doubt there is a place in such a organization for children. In a normal open world RPG where you expected to experience every aspect of life like marriage, and family, work, community, and so on the additional aspect of having children running about makes sense.
Skyrim did it but not well, there were only 2 models for kids in that game with 2 voices. DAO had only slightly better variances in models but still the same number of actors.