Why was Hannah's little brother scared in the car to Grandpa Will's?

Ron-ron was afraid he would make a mistake during the "Four Questions".

The Four Questions aren't that hard."

"I can't remember all four questions." Aaron almost shouted the last word.

"You don't have to remember them." Hannah's patience was wearing thin. "You're supposed to read them. From the Haggadah."

"What if I can't read it right?"

Hannah began to sigh, caught herself, and turned it into a cough. "You've been reading right since you were three, Mr. Smarty." She cuffed him lightly on the side of the head and he cried out.