I am actually writing an article on this very topic!
One of the best things I've started doing lately for multiple day trips is to pack luggage by the day, not the child. (I have five children, plus myself & hubby to pack for.) This reduces the amount of luggage you have to "lug" in and out of the car.
When staying several nights in one place, I put the children's outfits by day into one grocery bag - one outfit per child into one bag per day. A total of five outfits in one bag for my family, then tie the bag & labeled "Monday" or "casual". for example.