We should trust Christ instead of our own reasoning, of course, right. What did He say about little children?
"But Jesus called the children to him and said, "Let the little children come to me, and do not hinder them, for the kingdom of God belongs to such as these." (Luke ch 18, Matthew ch 19, Mark ch 10)
Since the Kingdom of God, Heaven (Matthew 19:14), belongs to such as little children
already, the question is how you and me can change and become more like them.
And we know we must in fact --
"At that time the disciples came to Jesus and asked, “Who, then, is the greatest in the kingdom of heaven?”
2 He called a little child to him, and placed the child among them.
3 And he said: “Truly I tell you, unless you change and become like little children, you will never enter the kingdom of heaven.
4 Therefore, whoever takes the lowly position of this child is the greatest in the kingdom of heaven.
5 And whoever welcomes one such child in my name welcomes me."
From these, we can surmise that just as others have written in this thread, God will show mercy to little children that die without having heard of Christ.
Consider what Paul wrote in Romans about those without knowledge of the gospel:
6 God “will repay each person according to what they have done.”
a 7 To those who by persistence in doing good seek glory, honor and immortality, he will give eternal life.
8 But for those who are self-seeking and who reject the truth and follow evil, there will be wrath and anger.
9 There will be trouble and distress for every human being who does evil: first for the Jew, then for the Gentile;
10 but glory, honor and peace for everyone who does good: first for the Jew, then for the Gentile.
11 For God does not show favoritism.
12All who sin apart from the law will also perish apart from the law, and all who sin under the law will be judged by the law.
13For it is not those who hear the law who are righteous in God’s sight, but it is those who obey the law who will be declared righteous.
14(Indeed, when Gentiles, who do not have the law, do by nature things required by the law, they are a law for themselves, even though they do not have the law.
15They show that the requirements of the law are written on their hearts, their consciences also bearing witness, and their thoughts sometimes accusing them and at other times even defending them.)
16This will take place on the day when God judges people’s secrets through Jesus Christ, as my gospel declares."
A fair and exacting standard that few adults could do well on their own....
So....What about little children then in light of this?
--> "... And where there is no law there is no transgression." (Romans 4:15)
13 To be sure, sin was in the world before the law was given, but sin is not charged against anyone’s account where there is no law. (Romans 5:13)