If you are coordinating or managing flights and schedules for multiple parties, then I would definitely book early so that there isn't any last minute scrambling to secure flights, seats, and meeting times and locations. However, if you're planning just for your own family, I would check the seat availability regularly (looking at several airlines), and if there were plenty of seats still open, I would wait, especially for a NON-high season like early May. The best prices should appear sometime around 45-75 days out. Like the PP mentioned, we having been seeing prices dropping to near $400 if you wait. Of course if oil prices start to skyrocket, airline tickets will likely follow.