I've been to all the above recently and for the teenage daughters, your only choice is Aruba. The Westin is very decent though not amazing. Unless your daughters like to read books at night or go to bed at 10 pm, Aruba is the only place that has anything to do. St. John is beautiful but quaint and quiet, Grand Cayman is also very quiet, especially in the area of the Westin. No experience with SPG in Mexico.