I've started to become a devotee of wearing golfing clothes (skorts/bermudas and sleeveless tops) to WDW. The link below shows some examples. They tend to look slightly more structured, "formal" and fashionable (while still pairing well with sneakers), and are also long-wearing, moisture-wicking and wrinkle-resistant. I don't wear a sports bra, but something similar: a tank style "Genie" bra that is lightweight and supportive despite not having an underwire.
On my feet, I go with running shoes with moisture-wicking socks for our hectic morning rope drop arrivals, and hiking sandals or Crocs (cute Crocs sandals, not the chunky clog-style shoe) for our more relaxed evening itineraries. Changing footwear at least once a day has helped me avoid blisters (so far)!
Also, I swear by the idea of packing just one outfit per day, using clothes that all follow a general color scheme so they're mix-and-match. I can pair the same couple of accessories (like a colorful crossbody bag and big vintage sunglasses) with every outfit, and I don't end up overpacking. Since I do all the packing for our 2 kids, I also pack the same shirt colors for them as I'm packing for myself -- we wear them on the same days and it makes them easy to spot if they start to wander off. Not everybody wants to be "that matchy family," though...
http://www.golfgalaxy.com/womens-apparel/search