The problem here is that chronology matters.
In Abraham's time, child sacrifice was common. Reprehensible, but common. As God had never delivered the terms of the covenant to Abraham, he would not have been bound by them. For lack of a better way of explaining it, Abraham shouldn't have known any better - why wouldn't sacrificing your child be okay? Abraham knew one thing, and one thing only - God was in charge. Whatever God said, you do. As such, it would have been, in Abraham's mind, completely legitimate for God to ask Abraham to do this. (And, obviously, God made his intention and position known to Abraham through this incident, but I understand your desire to keep to the facts before this happened.)
By the time of Chronicles, however, the covenant had been given, and God's position on Molech (the local rival god who demanded such sacrifices) was well known. For Abraham, just getting to know this Yahweh God, it is understandable that he would have been unaware. For, say, Manesseh to "burn his son in the fire" was an overt, intentional act favoring Molech over Yahweh.
Intentions - especially those guided by chronology - matter here. Abraham was being obedient, Manesseh was being defiant. There was a world of difference to the practicers that exactly explains the "contradiction."