Casual is fine
I have worn everything from jeans to business casual.
Not officially but usually, especially for dinner you dress on the nicer side, i.e. no t-shirts . For men nice jeans and a collar or sweater would be recommended. I dont know what to recommend for women, just look your usual nice self.
No but smart casual to business casual is appropriate and normal Jackets aren't required but people do wear them.
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