I would NEVER wear shorts to my office! 90% of the time it's a suit, and when it's not it's always a nice blouse or sweater with a skirt or slacks. I've worn khakis maybe 3 times in a year, and feel strange doing so every time.
As for the length of shorts/skirts, I like the guideline my kids' middle school came up with: Put your arms at your sides straight down. The fabric must extend past your longest finger by at least 1 inch.
DonnaP99