“...there is no place in the word that says that we are promised that all babies or children are going to Heaven.”
I think you miss the meaning of Mark 10:13-16.
Jesus Blesses the Children
13 One day some parents brought their children to Jesus so he could touch and bless them. But the disciples scolded the parents for bothering him.
14 When Jesus saw what was happening, he was angry with his disciples. He said to them, Let the children come to me. Dont stop them! For the Kingdom of God belongs to those who are like these children. 15 I tell you the truth, anyone who doesnt receive the Kingdom of God like a child will never enter it. 16 Then he took the children in his arms and placed his hands on their heads and blessed them.
In the Kingdom of Heaven, there is NO ONE but little children. (And adults who are like them.)
There Jesus was referring to the Jewish law that children (as were women) were exempt from studying the Torah.
What he is saying is that he, indeed, wants children to learn God’s ways, and that we should never prevent them from studying and walking with God.
So still it is not a universal promise that all children are going to Heaven and are saved.
Why is it important to understand God’s intent on this? To keep those children out? NO! Not at all. Because the more people who know the truth, the more people CAN be in the Kingdom of God.