As soon as possible.
Yes, Beach Cocktail Attire.
5:00PM - Ceremony Immediately followed by a Cocktail Hour 7-10PM Reception
If you are an American Citizen, you only need a valid passport (6 months before exp date). If you're not an American Citizen, please go to: https://do.usembassy.gov/dominican-republic-entry-requirements/ You will also need to complete an E-Ticket (customs declaration) before arriving in the DR. https://e-ticketdominicanrepublic.com/?msclkid=5ecf2d7467f71c50e58a4944e3e7f8f4 Once you check in for your flight, it will prompt you to fill out this doc.