We have just returned from Sorrento and had a private driver to and from Naples airport. Gianpiero Fiorentino comes very highly recommended! He charges 90 euros for the trip in a very comfortable mercedes van seating 7 people. His English is excellent. He also took us (2 adults and 2 children aged 5 and 6 yrs) on an excursion along the Amalfi coast which included visiting a Mozorella factory, olive factory, and took us to an excellent local Italian restaurant high in the mountains with wonderful views of Sorrento and the Bay of Naples.
He has his own website http://www.gianpierofiorentino.com
Highly recommend him!!