Neighborhoods to stay in

Venice - anywhere on the main island. It’s all pretty walkable. I personally like campo San Polo area - a bit away from the madness that is Rialto to San Marco but still close. Not too close to the Rialto Bridge though!!

Rome - historic core near Campo di Fiori/Navona/Pantheon. Easy walking many places, attractive, easy to get around, less traffic than other areas (more pedestrian streets).
Or Trastevere. A touch farther but a great area to hang out, good restaurants.

Thanks Mira! I will look into those areas for both cities/

For Rome, I agree with Mira.

For Venice, I also agree with staying in one of the less visited sestiere - Dorsoduro, San Polo, etc. Definitely stay away from the path between the station, the Rialto, and Saint Marks Square, unless you find Times Square too restful, too quiet, and lacking in sufficient numbers of tourists.

For Florence, look at the Oltrarno.

I recommend staying in the Testavere neighborhood in Rome. There are a number of good small hotels and family owned restaurants. It is a charming part of town and has tram connections to other parts of Rome. Taxis are available and affordable.

For Venice, the Dorsoduro - we stayed at the Hotel Galleria.

For Florence, the Oltarno - Santo Spirito neighborhood we rented apartment through VRBO.

Enjoy!

Thanks everyone! I appreciate the help. Got some options now for Venice, Rome and Florence. Any ideas or thoughts for areas/neighborhoods to stay while in Sorrento?

For Venice I recommend the Castello area. Away from the madness at Piazza San Marco and close to the Biennale. Check https://europeforvisitors.com/venice/venice-hotels.htm for more ideas.