I don't know that I'll be any help, Bijou, and you've gotten a lot of great ideas. But for what it's worth, I love shorts, and I wear them for appropriate activities from April/May into October/November.
Perhaps it's the climate, since my mother (ladylike and modest) always wore shorts in the summer, and even had plenty of smart casual shorts sets in the late 80s/early 90s. It's been a while since I've seen my grandmother in them, but she definitely wore them at her house when I was younger. So I've never grown up with a stigma about them, except for obvious places they, and other things, aren't appropriate.
I am picky about the fit. Mine are all denim and get worn in pretty quickly. Not tight in the crotch, and definitely not tight in the thigh. My thighs are not small, so shorter inseams tend to go with flared leg styles. The sweet spot is about 5"; anything longer is cut like a stovepipe and emphasizes my thighs, in addition to being horribly uncomfortable (hot and tight and restricting).
Right now I have three pair (two sizes) all in the same kind, a random brand and cut I found at Kohl's two years ago. They must have been a fluke, since I tried to get more but they were totally sold out in other stores and online. The fronts are non-stretch denim and the backs stretch! Very unusual, but perfect for me.
I almost always pair them with graphic t-shirts. I've got quite a few, they're easy to wash when I sweat in them (which I will), they're fun, and they have the right balance of shoulder fit, waist definition, and length to go untucked. Blousey blouses just aren't a good look with short flared shorts (at least not on me). I've got half a dozen pair of sandals, and sometimes basic white lace-up Keds.
I'll wear this sort of thing for all kinds of errands and shopping, choir rehearsal, Bible study, casual visits, and projects or laying around at home. Just my basic uniform that's always comfortable. (The biggest consideration is if I'll be somewhere with high air conditioning for an extended period of time!)