A family in their nightclothes.
nightclothes definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
clothes to be worn in bed, as pajamas
also night clothes
nightclothes definition by American Heritage Dictionary
Clothes, such as pajamas or a nightgown, worn in bed. Also called nightdress, nightwear, sleepwear.