You are correct. God does not send innocent babies to hell for eternity. If babies go to hell, they are not innocent.
According to Calvinism (and others to be fair), your children were conceived sinners, and are not innocent. They were in Adam's loins and participated in his sin. This is what Original Sin teaches.
But if this is a figure of heaven, why was there sin in the promised land? God was being merciful here, I agree but I don't think we could see this as a model of heaven. Do you think every single adult complained? I wonder.
Heaven is the "promised land" we wait for. The land of Israel was a figure or picture of this, a land flowing with milk and honey.
God caused all the Jews who sinned in the wilderness to die, except for Joshua and Caleb who did not sin. But God allowed the children to go in because they did not know between good and evil in that day.
If a three year old boy finds his father's gun and shots his sister, we do not try and convict that little boy. Why? Because he did not understand his actions. We got this concept from the Bible!
Yes, but nevertheless, God explained to Jonah that it was JUST AND RIGHT to spare Nineveh because there were 120,000 innocent children there. But if God had destroyed Nineveh, those children would have went straight to heaven, their parents would not.Yet God was ready to destroy them ALL if the adults did not repent.
Or maybe he was saying that he will go to his son in the grave - that there was nothing he could do now and his son was gone. Whether David's baby went to heaven - we don't know.
No, David said he would go to his son, and David KNEW he was saved, God promised the KING would come through his seed. David also had the Holy Spirit and wrote MUCH scripture (many of the Psalms).