I booked a stay for my family of 6 at the Grand Sirenis Maya in Akumal, Mexico. My husband and 18 year old twins are adults. For everyone 17 and under, they ask you to choose exact age at time of travel from the drop down menu. Our confirmation was received, and seemed accurate as 2 rooms- 4 adults - 2 children ages 15 and 16. After 11 hours a of travel, we checked into to our resort with our Booking.com confirmation and were told that we owed an additional $1500 for 6 adults.