The Greek word for, "Children", I Acts 2: 39, Is, "Teknon", It means children of an age of understanding, It means One born to a family, They could be grown up, Just like I ask a lady how her children are, And they are in their thirties.
Teknon has the same meaning as, "Ben" from Jer 31: 15, What Matt 2: 18 is quoting from., And neither of them mean infants.
The Greek word for, "Little children", Is "Pais"
If Acts 2: 39 meant infants, The Greek word would have been, "Brephos".
Plus, How can an infant, Hear the gospel, Believe it, Repent, get born again and chose to be baptised???, Because that is God's way for baptism.