Sure, but it's a closed hermeneutic at that point, since it presupposes an unfalsifiable. No useful discussion is thus possible. This touches on what yovargas said earlier--yes, the source of morality does affect the nature of the imperative.
Returning to the open discussion: morality is a self-perpetuating but flexible social construct. It codifies values a society designates as desirable, de jure or de facto. Some of these are, as yovargas notes, on the practical side: violence is always limited one way or another in moral codes. Others are designed to reinforce the cultural status quo: these often take the form of prescriptions of personal behavior (the concept of honor, clean/unclean, et al, but also consider things like the Food Pyramid). Many are somewhere in between. All share a social impetus that, when it works, makes those raised under it feel good when they do something "moral" and bad when they do something "immoral."
As a society becomes more complex, it becomes more self-conscious of morality and the need to codify it. Edicts emerge from taboos, laws from edicts. This is where I think the ladder system AJ describes becomes useful--it tracks how morality is approached, and the additional angles of attack, if you will, from which the feeling of good and the feeling of bad can be inculcated.
In regards to children's actions: young children experiment with behavior, being the social primates they are.

They pick up very, very quickly which behaviors are the most desirable, not just from overt parental action but from subtextual factors (tone of voice, posture, facial expression). So when they do something that gets positive reinforcement from a parent, it becomes part of their moral matrix just as quickly as if they do something that gets negative reinforcement. They tend to repeat the experiments until a strong enough trend is established, of course, much to our amusement and consternation. I know my kid often did something sweet and something annoying in the same breath when he went through the early part of that phase.