The answer I give at present is open to change. I usually begin with John 14:6. What it says is that no one, but no one, can possibly end up in heaven except through Jesus the Messiah. We should not add to Scripture by saying they can only get there by making a cerebral decision. We are not saved by making a decision (Satan can easily make us doubt that - "it was psychological, your mind could change," etc.) but by the Creative Love of God, by grace alone (Ephesians 2:8-10 taken literally).
That means babies who die the first week, retarded persons, ignorant persons, OT persons like Abrham,etc. can be saved by the Son of God. And when they get to heaven they will discover it was by Him resurrecting them in a heavenly body, and perfecting all that is missing of their perfected love.
In one sense the Spirit is the life force that brought all life (vegetable, animal, image of God life) into being by His creative power. The Creative Love of the Spirit is also open to anyone anywhere for every aspect of the inspiration we need. That means anyone can look to the Holy Spirit for wisdom, inspiration, etc. long before they come to personal faith in Jesus the Son. When someone in a Indian tribe a thousand years ago called on "The Great Spirit" and asked for wisdom, the Spirit did not say "sorry you have got the wrong number - get saved by Jesus first." Those who live by the Spirit will also be guided to respond to the Son when he is preached to them (as often happens in missionary situations - I saw it happen in India).
But the Creative Love of the Father, and of the Son (eg. in the Garden of Eden), and of the Spirit can be rejected. We can grieve the Holy Spirit.
We can refuse to be filled by the Spirit, etc. That means anyone who refuses the Spirit's help is missing out on the Creative Love of God. We don't have to say they are immediately sent to hell. Lots of Christians do without the Spirit for a time till they get desperate.
What governs our eternal life is explained in John 3:19-21. Anyone who would not be happy with the perfectd love of heaven inevitably excludes himself. But for anyone who would be happy with the perfect love of heaven, it is theirs already (the argument of C.S.Lewis' picture in The Great Divorce - which really got me moving in this theological direction).
What is said in John 3:19-21 applies to Jesus as the light that keeps coming (present tense) into the world (John 1:9). But it also applies to the Holy Spirit who enlightens, and to the Father whose light is the Creative Love that surrounds us. You cannot divide the Trinity as in the Evangelical theory that says you must first decide for Christ, then you get the Holy Spirit, and He gives you assurance of the Father's love. People can turn to the light via the Father or the Son or the Spirit, bu when they come in by the Spirit He will introduce them to the Son.
In my model there is no need to posit another decision after death.
Children of all nations are already in that Trinitarian light, which is why Jesus said we have to be like them. Children and retarded persons are naturally light lovers. It is only later than they can become self-sufficient, and by preaching we have to turn them (repenting is not feeling sufficiently sorry, but turning) to the light of the Father, the Son, and the Spirit (as Paul explains in Acts 26:18).
But all that is provisional explanation, an exploration, till someone
can offer me a better model to explain how the Creative Love of God works.
None of us is infallible, and I have already found my mind changed (continually
renewed as Romans 12:2) again and again.