St. Lucia, it is an increadable island. Basically made for lovers. Stay at the Sands resort. If you have deep pockets then you could even get one of the private cottages. They come with a beautiful view over looking the water, a private pool for fun time and a personal driver. The resort has a great night life, wonderful food, and unlimited activities.
Think of doing something new that you will remember forever. A safari to Africa is an experience of its kind. Specific place that you should visit include Lamu Island in Kenya and Zanzibar Island in Tanzania.