If you are looking to experience life on a private island, you can consider doing a resort excursion of your choice. You may check with various guesthouses and what resort excursions they offer. The price will vary according to how luxurious the resort is. Usually how a resort excursion works would be - you pay an entrance fee to the resort that you are visiting and some resorts may impose a minimum spend for the day for each person visiting. You will also need to pay a return transport fee to the guesthouse for sending and fetching you back to the island.