"Child" Christ is the newly reborn in the Teachings of Jesus Christ, the true understanding and fulfillment of God's Will, His Commandments. 
"Child in Christ" is a person who is just beginning to comprehend the breadth, depth and spiritual height of the Teachings of Christ about the Will of God, just beginning to discover for himself its practical significance, learning to apply it in his life, to live according to the Word of God's Will.
"The Child" is the new understanding of the "Son of God", the true Man, achieved, revealed, revealed to the nations by Jesus Christ. 
 "Child" is also a symbol of a sincere person, straightforward, not able to hide lies, without cunning, malice, wishing to follow the teachings of Christ to be morally and spiritually pure, not to commit unrighteous acts.
Negative Meaning. 
 "Baby" - a symbol of immature, spiritually frustrated man in the knowledge and fulfillment of God's commandments, unable to distinguish between good and evil, reasoning and guided only by feelings, emotions, carnal demands, urges. 
"Infant" is an image of a person spiritually weak, not matured in mind, inconstant, changeable in thoughts and actions, not versed in the teachings of the Prophets, Christ, the Apostles, who is not capable of spiritual work on himself.