It got me thinking that having a weekday uniform for mum's is not such a bad idea either. While I am not suggesting that you run out and buy a dark blue tracksuit for each day of the week, I think developing a signature style can really help out on those busy mornings.
The perfect example of a great signature style that is perfect for the school drop off is Elle McPherson.
Her signature look is made up of a denim bottom (usually a skinny leg jean), a knit top, a blazer/jacket/cardigan, a large scarf, big sunnies, and ballet flats. All of those items mix and match easily, and she adds punches of colour and pattern through the shoes and scarves. It really wouldn't matter what pieces she grabbed in the morning, they would all go together.
Of course, you need to pick a style that suits you. Elle's style is a touch too preppy for me, and I prefer to wear heels, but if I added a few vintage touches, it would work. Is your style more elegant, more sporty, more urban hippy? Take your style and then develop a "uniform" that fits that style.