Friday night will be casual - think sundresses (and flats) for girls and shorts/polos for guys Saturday is cocktail attire - girls can pretty much get away with most dresses - guys can do pants/button downs - no jacket needed (just no shorts or flip flops please!)
We definitely recommend booking the airport shuttle through the hotel. They use a company called Amstar. Please do not try and hail a cab or uber at the Cancun airport!
The resort has filtered water fountains so we recommend bringing an insulated water bottle to stay hydrated. We also recommend bringing a tumbler for poolside cocktails!