Or, if one parent becomes a citizen, then citizenship shoule be retroactive for their non-adult children.
Why? The law already allows for these non adult children to become legal permanent residents, the pathway to citizenship. Why should anything be automatic? What if these children are undesirables we don't want here, criminals, etc.? As it is they can apply for green cards and in almost every case will get one, and then in a few years they can become citizens provided they stay out of trouble, learn English, and pay the required fees. I'm not worried about the fees so much, but I'm all for encouraging immigrants to stay out of trouble and learn English. Aren't you?