I know you said that you believe all Children under the age of accountability will go in the Rapture, but is it not possible that God, who knows when we are still in the womb whether or not we will accept or reject his gift of salvation through Jesus, would take the children that he knows would have accepted, and leave the ones he knows were going to grow up to reject Jesus, to take all children it would seem very likely that he would be taking children that were going to grow to reject Christ.
According to my understanding of Romans 7:9, all children under the age of accountability belong to God and their sins are not counted against them. It’s true that God sees the end from the beginning. But for these children, the end that God has seen is their inclusion in the rapture, not some alternate end that will never be. (Can He even see an alternate end?) How could He justify excluding them on the basis of a decision they’ll never make in a future they’ll never have?
One could use that same logic to argue that since God knows who will become believers during the Tribulation, He should just include them in the rapture and save them all that suffering and persecution. But even though God is outside of time, we are not. We are subject to its constraints, whether for good or bad.