First call Casa sur tells us everything .

If it’s the child (or young person) who actually says “¡Ay pibe, por Dios!”, then it’s more like:

“Oh dude, for God’s sake!”
or
“Jeez, man!” / “Oh man, come on!”

In that case, the phrase is a reaction, not someone addressing the child.
It’s something young Argentinians might say when they see something shocking, painful, or unbelievable — like if a friend falls, drops something, or does something stupid.

So in natural English, depending on the emotion, it could be:

😮 Surprise: “Oh man, oh my God!”

😬 Frustration: “Jeez, dude, for God’s sake!”