Hi there, stcar. Some timing details?
He has to be in Assisi on Oct 9th so we were thinking of flying out on
the 2nd.
If you are flying from the U.S. then you won't land in Italy (Rome?) until the 3rd and it will take you some time to get to the Sorrentine/Naples/AC region so most of that day will likely be shot. If he's doing business in Assisi on the 9th, then you'll need to leave the area on the 8th to give yourself plenty of time to get there. That leaves you 4 full days and some ofd hours to play with.
I would do this trip by public transit: trains, ferries and SITA buses. Parking/driving in Naples and the AC is no picnic. It's not our thing for any number of reasons but some folks do parts of the AC by private driver.
I would also do this trip independently as there really isn't much there that requires or benefits from a guide, IMHO. The one exception might be Pompeii as it is a very large, complex excavation than can benefit from guidance to get around/understand...although we did it on our own with a book. Along with their other tours, the Mondo Pompeii guided walk has been very highly rated by RS posters who've taken it so take a look?
https://www.sharedtours.com
We stayed a few nights on the island but Capri is easily done one one's own. I will caution that unless willing to explore away from the small town centers - and as good walkers you certainly should - you'll be in the thick of the day-tripper mob most of the day. IMHO, skip the Blue Grotto: not worth the time and effort for the few minutes you'd get inside the thing. We chose not to do that one based on reviews and desire to escape rather than be surrounded by the throngs and have never been sorry. :O)
Although it's at the doorstep of versus IN the AC, Sorrento makes a good base for exploring the region due to it being a hub for bus, inexpensive commuter rail and ferry services. Aside from Naples, it also offers the most restaurants, hotels, shopping and other amenities many tourists find desirable. It is 30 minutes or so by Circumvesuviana commuter train from Pompeii and about an hour by the same train from Naples. Pickpockets? You'll just want to take the same precautions with your valuables on the train, in Naples, etc. that you will anywhere else tourists go/ on public transport they use in Italy. Do that and you can just relax and have fun.