beehive, your question is both noble and difficult to answer. There is ongoing debate as to exactly how God handles that, but ultimately that is for God to decide. We don't have to fear that they were just cast into hell forever, however. According to Hebrews, chapter 11 (New Testament), God credited the faith of those who lived before Christ, as righteousness. They are described in Hebrews 11, but if you could read all of Hebrews to get the context, that would be best.
How He credits that, I don't know for sure, but those who had listened to God and obeyed His commands were counted as faithful, or having faith, and received credit for it.
We, on the other hand have the blessing of looking back in history and reading the accounts of Jesus, "the Lamb of God who takes away the sin of the world." Because of that, our faith has to be in the final sacrifice of Jesus as sufficient to remove our sins. This is a personal, intimate decision that each person must make. I can't make it for you, and no one could make it for me.
As for the child who dies, the Scruptural base is that until a person reaches an age of moral understanding (or aware of right and wrong), they are deemed unaccountable for moral decisions. They are not innocent, mind you, just unaware of moral law. Although I cannot currently recall the reference for that statement, it is a firmly held belief which is based in Scripture.