The phrase "childlike grin" is correct and usable in written English.
It can be used to describe a smile that is innocent, joyful, and reminiscent of a child's expression.
Example: "She greeted him with a childlike grin that lit up the room."
Alternatives: "innocent smile" or "youthful smile".
'But, you know,' he says, grinning his mischievous, childlike grin, 'I am just saying it.
When you meet him, he looks at you with a wide, childlike grin, his head tilted slightly forward, carefully watching how his words affect you.
With all the talent we had sitting there on that bench, sending me?" And in his own corner, goalie Marc-André Fleury showed no bruises as he wore the childlike grin that is his signature.
With a twinkle in his eyes and a childlike grin, James continues.
His transitions were flawless, he switched vinyl with ease, and never seemed to miss a single beat; a childlike grin across his face with every cheer from the crowd.
Suddenly he was piloting the women around the empty drill court in so many expansive loops — extremely fast, with a childlike impervious grin.
But upon ending the interview, he couldn't even spin through 180 degrees to walk off to the clubhouse before we caught a grin of the most childlike glee spreading right across his coupon.
I left South Korea grinning, full of the childlike joy that comes when you dive into unfamiliar waters, struggle with the current and come up swimming.
Whitaker endows Amin with quicksilver mood changes, turning on a sixpence from terrifying bluster to grinning seduction and wheedling charm, and then to childlike paranoia and fear.
RICHARD D. ROSENTHAL With That Devilish Grin Richard D. Rosenthal was not a daredevil, but he did have a childlike adventurous streak.
Ansari's face conveys a childlike mix of naïveté and mischief, the stupefied look in his eyes ironized by a cheeky grin; his fans share his bafflement, and want to be in on the joke.
