We just got back from our first trip to Curacao. I found most of my info for the trip on Tripadvisor Curacao forums. We rented a car for the week (booked online) from local Just Drive. Small operation but easy and smooth rental and return. The only thing is you have a long walk to the end of the old terminal where their guy picks you up in their van. The rental office is about a block away from the airport.
We traded into the Royal Sea Aquarium and loved it! The Aquarium is next door and free if staying at the resort. We enjoyed watching the dolphins and sea lions. On the way to our resort we drove past Acoya but did not drive in. Important to note, Acoya is not on the beach. However, there are lots of pretty beaches you can visit. Some beaches are free and some have an entrance fee. Most beaches have a security guard which is good. Our favorite beach was a small beach called Kenepa Chikki (sp?) in the Grote Knip area. Kenepa beach and Cas Abou are also nice. Both Acoya and Royal Sea Aquarium are near Mambo Beach shopping area with many shops and restaurants. Be sure to spend a day downtown in Punda and Otrabanda. It was hot but one of those items we had to do while there.
Hope this helps! Have fun!