I'm writing this from roughly the standpoint I occupied at several points as a child. By "child" I mean from the age of 6 up through whenever. I do not have a very good standpoint from which to talk about parenting from the parents' perspective.
I wonder, if we noticed better that the child has a spiritual heart, might that lead to a more relaxed view of the parenting rules? Scheduling a child's life away and making it impossible for them to mess up with their diets and such seems, to me, rather inconsiderate to the child. Aren't they people who can make decisions too? If they are, then I would think it natural to assume that parenting cannot create the child, though it may mold the child. Same deal as discipleship.
When I was in a first grade Sunday school class, I asked me teacher how we knew the Bible was right (She'd asked how we know Jesus loves us, everyone else answered "because the Bible tells me so"). She was totally unprepared for the question, I hope: she answered with something like "because the Bible says so," which it was quite obvious to me was not at all a useful answer. I voiced my dissatisfaction with various things my parents signed me up for (some were good, others were, to me, intolerably chaotic). I have good parents--they listened.
If I had been signed up for things willy-nilly, and my parents had not listened to me when I told them I wanted out, I don't know how I would have ended up, but I do know that if that had been my life, it would not have been a life I could call my own in the way I can call the childhood I had mine.
Kids are people. Signing them up for everything under the sun without consulting them disregards their autonomy as persons. Disregarding them as unable to understand things, if you aren't even willing to try, will end up being a self-fulfilling prophecy. Kids live lives like yours, theirs just haven't been going for as long. They may doubt things, they may be passionate about things, they have joys and sorrows and frustrations. They need the Gospel the same as any of us. I know because I remember. I remember being afraid that God would miss something. I remember being afraid that God had not accepted me. I didn't really voice those worries, because I thought they were appropriate worries, but they were there. Why didn't I learn about what it means that God came to live and die for us? Why didn't I learn how Christ is Immanuel for us even today, when I was a little child? You can't believe for a child. Just because you are sure of your salvation doesn't mean your kid is. Just because a kid doesn't appear distressed, doesn't mean their theology is fine. How many grown-ups have flawed theology and don't even realize it? So also with children.
If you want a kid to make their faith their own, why wait until they're teenagers? Why wait for them to reach a certain age to start telling them how great God is and what he has done so that we can live without fear? They can understand a whole lot more than you think. Don't talk down to them, come down to them. It is not that hard. Have you forgotten who you were when you were a child? Do you think they aren't similar? Did you ever think you were merely a body to be exercised and fed, and a mind to be filled with facts? Didn't you consider yourself deeper than that all your life? I know I did. I had a love of learning, not just a duty to learn. I had subjects in school I did not like--I had writers I did not like. I remember being very irritated by my learning to read books (which seemed to think all kids were disobedient idiots) to the point where I practically refused to continue reading them.
Kids are smarter and more spiritual than people seem to think. They are people after all!