I find it hard to offer an opinion without seeing the rest of genderbend costume I'm afraid.
I would tend to lean towards the sandals, but I can't imagine walking in heels either.
I say post what you've got thus far and I'll offer a further opinion. If you can make the wedges LOOK like they're similar in construction material to the sandals, then I imagine very few will complain.
Also, let's face it, you're gonna get X complaints to begin with because you're being a "chick Luffy" instead of just crossplaying.