They try to hold it in and wait.

He grabbed the straps of his backpack and twisted them, feeling the palms of his hand chafe from the rope burn it gave him.

Jim was a big boy and had at least some potty training, but he was still unaccustomed to holding it. He had wet his diaper earlier, and even then what little he held in made him felt like he could explode any minute.

Marie seemed to feel the same way, biting her lip as her knees were shaking violently.