A.S.
Orlando theme park veteran here . . . I would never, I repeat NEVER wear sandals to WDW.
I wear hard-core, worn-in running shoes with good socks, meant to go the distance. It is a ton of walking, and in the heat the blisters can be fierce. I don't care how geeky I look. I pay good $$$$ to get into those parks, and I'm not about to ruin the experience by being physically miserable.
Good luck and have a great time.