First of all, you have to definitely book your venue at the earliest if you want to be there at a peak season (October - May). Is your event going to be outdoors? Then get the permits for alcohol and music beforehand. Transportation by ferry or boat is a great idea for your guests and let them know they should carry sunscreen, light wear, and comfortable shoes for walking.
Besides that, partnering with a reliable hotel such as the Havelock Island Beach Resort will be the icing on the cake in terms of easy and seamless coordination.