My former employer, Ford Motor Company, considered resort casual to be khaki (Dockers) type of pants and any collared shirt (including golf or polo type shirts) pants for men and capri, khaki, or linen pants or any type of skirt that wasn't a mini skirt and non t-shirt type tops for women.
That being said, I would wear a nicely coordinating colored tee shirt with a pair of capri pants with a sweater around my shoulders in case it gets cool and consider myself dressed fine for "resort casual."
I think the main thing- (wait I need to zip up my non-flammable pair of shorts)- is no shorts or t-shirts with sayings, etc. anywhere at dinner.