@ milgreen2 and Pat and jaimeelsabio: I've combined some of your suggestions...thanks! mml, I've been to Cefalù and Villa del Casale, but thanks.
Castellammare del Golfo has been on my mind since before our trip to Sicily last year! It had fallen off my list because nobody ever mentions it. I agree that it's in a great position, but I wasn't sure if it was too scrappy (no aversion intended). The reason that I was considering the area around Cornino and Cortigliolo (just north east of Trapani on the coast) is that there are some interesting Airbnbs and quiet beaches in the area. April not being beach weather, but still nice to walk.
We will be arriving from northern Italy after having spent 20 days in Venice, Bologna and Milano so we'll be looking for a slower pace. We're ending the trip in Napoli (3 or 4 nights, yet to decide) and Rome 4 nights (booked).
On the island, I guess we'll need to move more often than I'd hoped. How's this sound? I keep seeing ways to shuffle this around. BTW We've visited Palermo before but just for a day.
Fly into PMO, pick up the car sleep in:
Castellamarre 4 nights (visit Scopello, Zingaro, Segesta, San Vito lo Capo)
Trapani (or close-by)?: 3 nights (visit Trapani, Erice, an Island?)
Mazara del Valo: 3 ( Marsala en route, Dancing Satyr and the town, Selinunte, Sciacca or see en route to Agrigento)
Agrigento 1 (Scala dei Turchi en route to Agrigento). Valley of Temples at sunset
Palermo 2, or 3 here and 3 (instead of 4) in Naples ??? = 13 or 14 nights
Fly to Naples 3 or 4 nights (never been, need to see Pompeii, Herculaneum, Archeological Museum)
Ending in Rome 4 nights (booked, it's our third visit there)