A good rule of thumb is to book your photographer early. Like even 3 to 6 months early. Then you know you have that locked down and in place. Your favorite photographer might book up, but going zip lining for instance can usually be booked with in a day or 2. When choosing a day for a photo session you want to be able to first check in to your hotel, get settled, enjoy your surrounding for a day or 2, work on your tan just a bit, and then have your session. You want to book it in the middle of your trip. Make sure to have your photo session at least 2 or 3 days before you leave the island. Maui has great weather, but sometimes it does rain and you have to reschedule. Give yourself some wiggle room so you and your photographer can find a new time that works for both of you.