When I'm going to see students but am not actually going to be teaching, I always want to dress down a little, to signal that this is a time when I'm not "on" and we can interact as equals.
Wearing shorts is always a bit iffy for me, as they often make me feel self-conscious. But taking inspiration from academichic and What Would A Nerd Wear, I added an embellished white top and a belt.
Top: Calvin Klein Jeans via Costco
Tank top: ancient
Shorts: GAP outlet
Belt: L.L. Bean outlet
Sandals: Nine West
Earrings: inherited from my grandmother