I live in sundresses while at Disney! I tend to favor tech fabrics b/c they are great in the heat and humidity. Prana makes some really cute, fashionista friendly dresses and if you look you can find them for better than retail prices. (backcountry.com, rei.com are my go to websites!)You just have to keep an eye out for sales. Lole also makes some great tech fabric sundresses, very cute and swingy. Athleta.com has the best "sport" dresses out there, but they are PRICEY. Sales are good though if you can catch them! Patagonia's Bandha dress looks really dressy even though it's a stretchy tech fabric. There is a longer version and a shorter version. Both really cute and flattering!!
As for shoes I am a flip flop person. Teva mush are my mainstays. I have never had a problem wearing them while at Disney. My feet have never bothered me at all. I also have several pairs of Privo flip flops. A bit dressier, more sturdy...but still comfy...although most Privo flip flops don't perform well when they get wet, as in caught in a sudden and very fierce rain storm! They get wet and stay wet for quite a while. If I want to get super princessy and go for the sparkle I LOVE Yellow Box flips! Lots of sequins options!!
Being at Disney does not sway me from my desire to look cute and fashionable whilst avoiding the pitfalls of humidity and sweating!
PS-I ALWAYS have my favorite hoodie with me in my backpack. The AC at Disney is STRONG and you will freeze if you don't have something to put on while inside!!!