Jesus came to fulfill the law, offering his own body as the perfect sacrifice, without spot or blemish. The blood of Christ was necessary for the atonement of sins and the redemption of mankind.
Jesus was crucified from the foundation of the world. Yes, it was the original plan.
"Knowing that you were not redeemed with corruptible things, like silver or gold, from your aimless conduct received by tradition from your fathers, but with the precious blood of Christ, as of a lamb without blemish and without spot. He indeed was foreordained before the foundation of the world, but was manifest in these last times for you." (I Peter l:18-20 NKJ)
Tell me, then, why do your children need to be baptized?