The answer for your dirst question is "it depends". Topsiders serves a buffet breakfast, but the restaurants have kitchen service. My memory is short without my navigators at hand, so I don't recall which restaurants serve breakfast. Lunch on Castaway Cay is definitely buffet. But, again, there are some days where lunch is buffet style and some that you can order from a menu. Don't shoot me for not remebering which right now.
Casual is fine, they just ask that no bathing suits be worn and shirts are a must.
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