I agree that it's perfect to visit Paestum from Salerno. I've never been to Atrani, but I think you are giving too much time to a single area of Italy. I've slept in Sorrento, and really looked forward to our day trip to Amalfi and Positano. But I just didn't find that much "to do" in the towns themselves. I thought Ravello was exceptionally attractive, but I wouldn't have wanted to sleep there more than a night or two, except maybe during the annual music festival.
I agree that Capri is magical, but its partial overlap with Positano (i.e. endless high-end Euro fashion and cosmetic boutiques ... ) takes away from Positano if not somewhat from Capri. Capri is so pedestrianized that it takes much more time than the mainland - I'd take nights away from the AC and give them to Capri, if you can afford it. Make sure about transport of your luggage to your Capri hotel. (I haven't slept on Capri, but have been there twice.)
Sorrento is perfect for those daytrips, and has the best transportation options. Be aware that there are three more famous ancient sites, much smaller, in the immediate area. (We got a five-site ticket and went to three of them, including Pomp and Herc.) We had one (satisfactory) over-100 Euro p.p. tasting meal in Sorrento, but it just isn't a "destination" for world-class restaurants. I admit that I haven't seen the actual question lately, but Sorrento is the past subject of many a Trip Advisor post from the UK asking, "How much is a Pint?" I certainly don't rate the AC beaches as remotely as good as the Caribbean or the U.S. east and west coasts.
Look into the public bus excursion from Sorrento to Sant Agata Sui Dui Golfi, and walk back down, 99% paved sidewalks.
Maybe if you go to Italy every three years anyway ... ?? ... but I just can't see devoting an entire vacation to the AC.
