Sorrento to Ravello, Amalfi and Positano

Even if I were experienced with scooter there is no way I would drive on a scooter or any other vehicle on the AC.

Positano doesn't need more than an hour or 2. I'd combine it with Amalfi and Ravello.
Leave the most amount of time for Ravello.

No interest in Pompeii?

Skip the idea of a scooter in that area.

Check the weather before you determine your travel plans. We were in Sorrento/Amalfi Coast last May and it rained the entire time with high winds that made taking a Ferry to Capri impossible. I looked to see the weather over the next week and you have good days on 5th-7th and the 50+% chance of rain with winds on 8-9th. Take the ferry to Capri on a good weather day. I agree with the other folks that renting a scooter and driving will be a bit of a challenge and you won't get a chance to enjoy the view.

I rented a scooter to tour the south side of the Amalfi peninsula and loved it. I found it very easy to drive, park, avoid traffic jams. I never felt unsafe and Highly recommend it if the weather is nice.

I’ve no doubt getting around by scooter will be a… unique experience. I’d only say that viewing the coast from the deck of the ferry was in some ways the most satisfying part for me. Pulling into Positano and Amalfi via ferry was magical. Your itinerary is completely reasonable. Wouldn’t worry about making extra time to explore Sorrento. As pleasant as it is, there’s not much to the place. You’ll get everything out of it in your mornings/evenings.

Have you used Google Maps to estimate time and distance, elevation to Ravello? Positano will need a parking space for 2. only one 2-lane road, heavy traffic, curvy, no guardrails, steep drop offs. You won't want to drive to Positano twice.