On our daughter's birthday, she wore her Aurora gown for our post-nap afternoon/dinner visit to the Magic Kingdom. She wore pink Tevas with it (I let her change into plastic Princess shoes for dinner only, as she was going to meet the princesses at Cinderella's Royal Table). I had a spare shorts/tee outfit in my purse into which she could change if she got itchy or hot in the gown, but she opted to keep it on for the rest of the night and clearly felt very beautiful and glamorous, dancing, skipping and twirling frequently as we walked through the park.
I think the primary considerations for a successful visit to the parks in a gown are: (1) make sure your daughter has comfy footwear suitable for walking long distances, and that her gown is short enough that she can walk in it easily -- the biggest issue I observed with other little princesses was that they were limping around in dress shoes, or tripping over their dresses); (2) have a back-up outfit on you so she can change if she likes (and a wadded-up plastic shopping bag, in case you need to carry her gown around once she changes -- they get glitter on everything!); and (3) if you are concerned about the gown getting wet or your daughter's hair getting messed up, plan an itinerary that avoids rollercoasters and "wet rides," etc.
Appropos of nothing, here is my darling princess in her gown and sandals in the Winnie the Pooh queue that night, in the midst of calling out something to the effect of, "Mommy -- look! The sign says it's a Hunny Potty!" Yes, we're working on her reading, and no, she made no attempt to
use the Hunny Potty as such...