Kelly Jeanie, I'm not sure if I'm allowed to post Etsy links here, but I found a seller there who makes apron style 'princess dresses.' It's quite literally a fancy little apron in the style of Disney princesses. They are made of cotton too, so I feel like they are more breathable and less itchy (a complaint my 6yo always has). They are also very easy off should she want to take it off, or say they fall asleep riding back to the hotel.
What kind of weather does WDW deal with in October? We're taking our first trip next year and I would love an idea as to what kind of clothes I should be packing