Blueeyedcod

Your plans sound great and your Naples hotels are very close to one another and are excellent locations. It's almost a coin toss for me as to which one I would choose.
Your rental car pickup and drop off plans are very wise as you will avoid ZTL's and it's easy to get to Positano from the airport as you're straight on the autostrada.
There is a very very long road tunnel just before you hit Sorrento and it has a low speed limit (60kph from memory) so make sure you stick to the limit as there are speed cameras in the tunnel.

jft

I booked a new b&b in Naples near Toledo Metro called Factory Design (looks great and very economical)for 3 nights and the VRBO 3 bedroom apartment just above Positano that comes with a parking spot for 4 nights. Booked Locanda di San Martino in Matera (thanks kja) for 2 nights. Tentative cooking class for the 6 of us at CooknfunwithMary in Matera for one evening. Waiting to hear back from the Matera guide now that we have a new date. Just Rome left- will look for something near the train station where we drop off the van.
Isabel, your photos of Amalfi coast,Naples and the various ruins etc are amazing! I saw them on another recent Italy post.
Blueeyedcod- thanks for the speed limit tip- with 3 grown sons as back seat drivers we should be okay!
I am really pleased so far with how things are coming along. I know the trip is ambitious with respect to the time alotted but I think its doable. With Amalfi coast after Naples,there will be some down time.
I am toying with when to go to Pompeii-either by train while in Naples or on our way to Positano from Naples airport in the minivan (worry about luggage in minivan and extra driving stress enroute to Positano). I would love to go to Paestum but will play it by ear.
I find this forum really helpful and appreciate the input given by all of you.
Thanks!

kja

I think there are luggage lockers at Pompeii, but I don't know for sure and if there are, I'm not sure what size....

jft

Looks like there is free luggage check at Pompeii entrance just after ticket booth.. I think it would make sense to go to Pompeii after we get rental car at Naples airport on way to positano..... That would leave 2 full days for Naples plus arrival evening......

Blueeyedcod

Yes, there is a left luggage room at the Porta Marina ticket office. Take everything out of the car - not just your luggage - and leave it there for the duration of your visit. It is free.