I do firmly believe there is biblical support for the fact that babies, little children and the mentally disabled do not go to hell.
Romans 7:9 For I was alive without the law once: but when the commandment came, sin revived, and I died.
Paul is speaking personally here. He said that he was once alive without the law, but when the commandment came, when he was able to comprehend what God's commandments are, then his sin nature awoke, as he rebelled against the commandments and therefore spiritually died. I cannot see this text making sense in any other way, but that, as innocent children, we are spiritually alive, but once we comprehend God's commandments, our sinful natures hold true and we then spiritually die.