I disagree, I think three weeks is great! I would suggest staying at the Villa Rosa in Ravello (really midway between Ravello and Atrani) Link here:
http://www.residencevillarosa.it/main.php?lang=en
Atrani remains largely untouched by tourism, and the Villa is furnished with kitchens and there's a pool on-site, so you can really relax and enjoy the view. Beautiful, beautiful, beautiful.