That’s up to you! The resort the wedding is at (and we encourage you to stay at) accepts USD and is also all inclusive. So you really won’t be needing to pay for anything unless it’s an extra once you arrive! Your local bank should be able to provide Pesos as well if you decide to exchange before the trip.
http://occidentalgrandxcaret.com
https://traveladdicts.net/vacation-made-simple-occidental-grand-xcaret-riviera-maya/
Yes! They have only the 2 prong outlets (no three prong).
https://travel.state.gov/content/travel/en/passports/how-apply.html
https://www.barcelo.com/en-us/occidental-at-xcaret-destination/?gclid=EAIaIQobChMI2PX3gOq_8AIVxd7ICh0AWg10EAAYASAAEgKw0_D_BwE
Internet is free, but not WiFi. Bring an ethernet cord for the free WiFi.