All transportation from the Cancun airport must be pre-arranged. (There isn't a taxi stand, and there isn't Uber in Cancun.) If you do get to the airport without transportation pre-arranged, then someone will be happy to "pre-arrange" it for you on the spot, for about double the price.
Once you're at Puerto Juarez ferry terminal, you will buy your UltraMar ferry tickets (round trip = ~$25 usd), and the ferry departs every 30-60 minutes. The ferry only goes to Isla Mujeres from the Puerto Juarez terminal, so you don't need to worry about taking the wrong ferry.
When you arrive on Isla Mujeres, there is a Taxi Stand to the left of the Ferry Terminal. All taxis on the island are red. Taxis can carry up to four people and their luggage, and should cost $150 pesos per taxi. You can get to the venue by name "Casa Camacho, en Punta Sur."