We need to look at Christ's Great Commission. Just before He gave it, covenant children (paidas) had been praising Jesus. He Himself had then insisted that God had perfected His praise — even out of the mouth of speech-less in-fants (nepia) and unweaned babies (thelazonta). Indeed, He soon went on to assure especially the tiny children in Jerusalem that He loved them just as much as a mother hen loves her own little chickens.
Soon after that, Jesus obviously included such speech-less in-fants (and other children too) — among the God-praisers in "all the nations" to be baptized in terms of His Great Commission. For, as Isaiah predicted of Him — "so shall He sprinkle many nations," and "He shall see His seed." Hence, Jesus commanded His Ministers: "Disciple all the nations, baptizing them!"