We can't save someone (or rather...well, we can participate in a way: see last verse below) -- only God can save, and we know the way is through Christ....
Before those verses about others working for our benefit (to call on or help bring God's grace) in particular, let's look at what you can do for others in a different way, since infant baptism is a question where we have to infer ideas about.
So, consider whether others can be a part of the process:
14 How, then, can they call on the one they have not believed in? And how can they believe in the one of whom they have not heard? And how can they hear without someone preaching to them?
15 And how can anyone preach unless they are sent? As it is written: “How beautiful are the feet of those who bring good news!”
16 But not all the Israelites accepted the good news. For Isaiah says, “Lord, who has believed our message?”
17 Consequently, faith comes from hearing the message, and the message is heard through the word about Christ.
18 But I ask: Did they not hear? Of course they did:
“Their voice has gone out into all the earth,
their words to the ends of the world.”
19 Again I ask: Did Israel not understand? First, Moses says,
“I will make you envious by those who are not a nation;
I will make you angry by a nation that has no understanding.”
20 And Isaiah boldly says,
“I was found by those who did not seek me;
I revealed myself to those who did not ask for me.”
21 But concerning Israel he says,
“All day long I have held out my hands
to a disobedient and obstinate people.”
1 I ask then: Did God reject his people? By no means! I am an Israelite myself, a descendant of Abraham, from the tribe of Benjamin.
2 God did not reject his people, whom he foreknew. ...
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Ok, I tend to want to just keep reading, but this helps us notice the really interesting thing that for those old enough to hear the word, during this life, someone has to bring it to them.... Or alternatively, if someone did not bring it to them, still there can be a chance:
18 For Christ also suffered once for sins, the righteous for the unrighteous, to bring you to God. He was put to death in the body but made alive in the Spirit.
19 After being made alive, he went and made proclamation to the imprisoned spirits—
20 to those who were disobedient long ago when God waited patiently in the days of Noah while the ark was being built. In it only a few people, eight in all, were saved through water,
21 and this water symbolizes baptism that now saves you also—not the removal of dirt from the body but the pledge of a clear conscience toward God.
e It saves you by the resurrection of Jesus Christ,
22who has gone into heaven and is at God’s right hand—with angels, authorities and powers in submission to him.
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Hallelujah.
And we notice in verse 19 He went even to the dead, that they might have a chance to turn and be saved....
So, here in this life, others can indeed be part of the action of God, by His Grace, such as for instance to tell the word of Christ!
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38 Peter replied, “Repent and be baptized, every one of you, in the name of Jesus Christ for the forgiveness of your sins. And you will receive the gift of the Holy Spirit.
39 The promise is for you and your children and for all who are far off—for all whom the Lord our God will call.” (Acts chapter 2)
1 Corinthians 7:16 How do you know, wife, whether you will save your husband? Or how do you know, husband, whether you will save your wife?
But I'd not worry for a child that dies without having been baptized, because consider 1 Peter chapter 3, as above. God will not be blocked by the mere decision of a parent whether to baptize their infant, or the failure to do so. God will decide, in His mercy and Grace, not dependent on us, to save.
