Amalfi coast

I hope others chime in. I haven't been there but I keep hearing from friends (that I trust) that the islands of Ischia and Procida are wonderful. Positano is a great shopping town, with a decent beach. Amalfi Town is far more rustic and (in my opinion) more interesting.

Really wouldn't call Positano or Amalfi rustic by any stretch.

neither are reasonably priced either, Sorrento is less expensive than either though also not a low cost place to stay.

There are definitely smaller towns along the coast but most are very small, lacking many options for swimming/eating, etc... but may be good for relaxing with an amazing view and I am sure there are so good values for some of them as well.

Personally I loved Positano, think it has the best view, best beach, very fun to explore as long as you don't mind steps and recommend it but it is pricey, especially with a group..
If you want only relaxation, choose any rental Villa on the coastal drive between Positano and Amalfi town.
Many look to Praiano as an option, but the area is really small so anything along the road SS163 to me would be fine.
Would be nice to have a short walk to a bus stop, even if you have a car as parking where you might drive to from your lodging will be a challenge.
For any ferry services, you will need to be in Positano or Amalfi to catch those.

The island recommendations are also good though not considered the Amalfi Coast, another option is the town of Ravello which lies above Amalfi and a very relaxing and beautiful place though not sure how reasonable Ravello lodging is ; I suspect no different than the town of Amalfi in terms of cost.

We stayed in Sorrento for five nights because of convenient day-tripping. But it's wrong to think of Sorrento as a bustling city (like Rome?) from which you might need relief. Although many posters here mention less expensive hotels they used, I think of Positano as a high-end destination, but with a few small, STONE beaches. (Sorrento has one, unattractive and crowded sand beach, with fumes from the Port.) What is your definition of "to relax"? Are you talking about 6 people and 3 rooms?

You have clearly asked about the AC, but I agree with the "island" suggestion. We visited Capri, but didn't try to sleep there. Even in September, it is getting late to book the AC. You may have to take your fifth choice of hotel, wherever you go. If food and budget are important, I would not rule out Naples. I'm sorry we didn't have time for the palace at Caserta. But I think you want the coast - at least Naples has a port and ferries.

When you research islands, check on the amount of walking. Capri, in particular, is HIGHLY pedestrian-only in most areas. I count that as a plus ...

.I have been going to Ischia for 14 years!! Only in last 2-3 do I find Americans. Be prepared to feel like you are really on vacation! Lot's of Germans, Brits, Some Russians and Nordic travelers, and a few Aussies :) mostly Italians of course:)

About 1 hour ferry to Ischia from Sorrento. Island life is always different than the coast...there are a lot of historical sights, beaches, cute towns, great gardens, hiking and of course being a volcanic island, spa hotels and hot springs in parts of the sea water.

It is a large island with four major towns, 20 minutes drive between towns roughly, you should consider renting a car/van. You cannot bring rental cars on to islasnds.

It has real sandy beaches that are easily accessible, unlike Sorrento.

If you rent a car....Try Baldesteri in the port on the left as you walk into town 1 block from ferry. There is a boat tour of the island from the main port town, it gives you a small stop in each of four towns.

Procida is beautiful but very small and with a large party I don't recommend it. Too small and does not compare to Ischia. Also lot's of walking necessary on Procida.

Ischia has a bus system but it is slow and insanely packed. Driving is easy just one big loop! Parking is not easy, just pay for a lot and relax!

Enjoy!

I know about this only because we drove by/through it on the way to the Naples airport from Sorrento in March, but the little hamlet of Vico Equense might be a good choice for you. It's halfway between Sorrento and Castellammare di Stabia, about 30 minutes away from Sorrento, and looks like it's on a little inlet. Absolutely gorgeous, better views than Sorrento for sure.

Have no idea about hotels, activities, even the town itself. Chime in if anybody knows about this place. Next trip to the peninsula I want to stay there.

Not true that ferries only stop in
Positano and Amalfi - different companies have different routes.

I like Minori or Praiano.

I love Marina del Cantone. VERY small. Right on the water. Several good restaurants, and a Michelin-starred place right up the road. Check out Hotel La Certosa as a place to stay. You can walk a few feet to the dock and catch boats to Capri, Positano, Amalfi. Totally skip the traffic. You'll feel like a rock star.

I found Sorrento a great place to relax.( I arrived there after a week in Rome so that may have something to do with it.)

If the group is then just being in Sorrento can be relaxing.

If you have to move to get away from them, then you will need to research the towns along AC for what you define as "reasonable"