I just came back from the Marriott Resort and Spa in Marco Island and highly recommend it. This place sits right on the beach where you can see the dolphin swimming in the Gulf of Mexico from your hotel window! They have two pools, two tiki stations for drinks and food. They also have an upscale restaurant called Kurrents, abolutely delicious food and great service.
Naples is only a half hour away. We also drove to Everglade City to ride in an open airboat and see the alligators! That was about a half hour away as well.