This is the 5872nd most frequent Japanese word.
ほっぺた
Cheek.
In this sentence, 'ほっぺた' refers to the physical cheeks of the children, emphasizing their appearance affected by the cold weather.
子供たちのほっぺたが寒さで赤くなっている。
The children's cheeks are red from the cold.
Here, 'ほっぺた' represents the surface of the cheek where the chocolate is present, making the sentence more visual and setting the context of his carefree attitude.
彼はほっぺたにチョコレートをつけたまま笑っている。
He is laughing with chocolate on his cheek.
This phrase uses 'ほっぺた' metaphorically to express extreme deliciousness, as though the enjoyment reaches to the extent of affecting one's cheeks.