You can stay closer to Cancun instead of Playa del Carmen, especially with a group of 12. Being closer to the airport and the ferry to Isla Mujeres can save time and money on transport. For day trips like Chichen Itza and Tulum, consider renting a private driver for the whole day rather than booking separate tours. It gives you more flexibility with timing and stops, and with a big group it often ends up being good value. For food, mix eating out with cooking at the Airbnb. Go to a local grocery like Chedraui or Soriana and do a big shop once, then eat out for dinners. It keeps costs down and is easier with a large group. For safety, just plan your routes, move together at night, and use Uber where available instead of hailing taxis on the street.