You're going to a once in a lifetime event wearing a "nice" polo shirt (whatever that is) and khakis?
The guy who comes into my office to service the copy machines wears a polo shirt and khakis.
Put on a decent shirt and sport coat. And the term khaki is ubiquitous. You want cotton or linen, not canvas. And what about the shoes. Shoes may be the most important thing, but no no one ever brings them up.
Time to step up your game a bit.