shorts as long as they are nice and I'm not sure the definition of nice is that strict. Here's how this site describes the dress code for signature dining:
For the Signature Dining Restaurants, a "Business Casual" dress code is in effect:
Men - Dress pants, jeans or dress shorts and a T-shirt or long sleeve shirt with collar is required. (Jackets optional.)
Women - Jeans, skirts or dress shorts and blouse, sweater or dress is required.
NOT PERMITTED: Tank tops, swim suits or swim cover ups, hats for gentlemen, cut offs or clothing with rips/tears are not allowed. T-shirts with offensive language/graphics will also not be permitted.
Victoria & Alberts has a stricter dress code and it is enforced.
I wouldn't hesitate to take a neatly dressed child in shorts to Jiko.