how should I dress? so do I go casual or semi-casual?
Casual. You want to be comfortable. It's also July; you want to be cool, too.

should I wear a polo? should I wear a T-shirt?
Either/or; polo's look great with a kilt, so do short-sleeve Oxfords.

(if so what color)
Speaking for myself that'd be a no-brainer; green.

Black belt or Brown Belt?
Black or brown sporran?
Either; I often wear brown with my saffron kilt.

Dress shoes or Chucks?
Which is the most comfortable? You'll be on your feet all day, and probably walk ten miles.