How does Lee use humor to soften the seriousness of the prank that was played on the two valuable sisters on the previous Halloween?

Lee informs the reader a the end of the story that all the kids were in the the prank by noting that after the sheriff sent out the bloodhounds; the children all put on their shoes to escape detection. I'm not sure that would work, but it does show the children suddenly becoming nervous.

"When Mr. Tate set them in motion three times, he finally guessed the truth. By noontime that day, there was not a barefooted child to be seen in Maycomb and nobody took off his shoes until the hounds were returned."