Children’s book midnight feast and fly in ear

I’ve been trying to remember the name of a book I read in the 80s for children / middle grade where a brother and sister are up after bedtime, one of has a fly or bug in their ear they are tying to remove , and they are caught by their younger brother. They don’t want the younger brother to tell their parents they were up after bedtime, so they try to make things as wacky as possible so that when the little brother tells their parents in the morning, they will think he was dreaming. One of the things they did was have a midnight feast. The plot worked.

I’d be very grateful for any help identifying the book / title!