Adam and Eve were perfectly capable of having offspring in the Garden, otherwise the commandment to be fruitful and multiply would be completely meaningless and God does not contradict Himself.

Also, after the fall, God says to Eve: Unto the woman he said, I will greatly MULTIPLY thy sorrow and thy conception; in SORROW thou shalt bring forth children... (Gen. 3:16 KJV) - thus, conception was possible before the fall, but was a more rare event, and childbearing seems to have been much less painful.

The childlike state of Adam was not permanent, and God wanted to educate him Himself, as Adam was God's son, bearing the title as a direct personal creation of God. "Who told thee that thou wast naked?" (Gen. 3:11 KJV) - the question is who; it does not preclude the possibility of Adam's learning about it from his Creator later.