Why do you despise God's grace and require human choice instead?Augustine believed re the pains of endless hell that those "of children dying unbaptized will be 'most mild of all'; but for all the chastisement will be eternal" (p.485).
(J.N.D. Kelly, "Early Christian Doctrines")
Or will such children all be forced by Calvinistic irresistible grace into heaven, without being allowed to make a freewill choice for or against Christ? Are they the lucky lottery winners over those in "hell" who weren't so lucky as to die in infancy? Salvation is, then, just a matter of pure 100% luck. And the Sovereign Omnipotent God Who is Love is the lucky lotto winner dispenser. If He loves you, you win the lotto. If not, too bad, he decided to let you fry alive forever. And if He chose you to die in infancy & therefore win the lotto, He doesn't care about your freewill. You'll be forced like a robot or puppet to do His will.
https://www.biblegateway.com/passage/?search=2+Samuel+12:16-23&version=ESV
2 Samuel 12:16-23 English Standard Version (ESV)
16 David therefore sought God on behalf of the child. And David fasted and went in and lay all night on the ground. 17 And the elders of his house stood beside him, to raise him from the ground, but he would not, nor did he eat food with them. 18 On the seventh day the child died. And the servants of David were afraid to tell him that the child was dead, for they said, “Behold, while the child was yet alive, we spoke to him, and he did not listen to us. How then can we say to him the child is dead? He may do himself some harm.” 19 But when David saw that his servants were whispering together, David understood that the child was dead. And David said to his servants, “Is the child dead?” They said, “He is dead.” 20 Then David arose from the earth and washed and anointed himself and changed his clothes. And he went into the house of the Lord and worshiped. He then went to his own house. And when he asked, they set food before him, and he ate. 21 Then his servants said to him, “What is this thing that you have done? You fasted and wept for the child while he was alive; but when the child died, you arose and ate food.” 22 He said, “While the child was still alive, I fasted and wept, for I said, ‘Who knows whether the Lord will be gracious to me, that the child may live?’ 23 But now he is dead. Why should I fast? Can I bring him back again? I shall go to him, but he will not return to me.”