Apertivo in both the Sorrento/Ravello and the San Gimignano/Siena/Chianti areas
Agree with barberinbee. Sorrento likely has a large selection of bars, and Ravello does have a few comfortable bars near the duomo, where you'll be able to order the usual Campari, Aperol, and Punt e Mes, etc. Not sure what kind of aperitivo snacks you'll find beyond olives, maybe some taralli.
I don't think of scenic Campania or rural Tuscany as being apertivi country. I associate apertivi with the hip urban centers of the north. I've enjoyed (expensive!) pre-dinner cocktails in the fancy hotels with the great sunset views along the Amalfi. I almost never drink before dinner in rural Tuscany, although I will have a Negroni in Firenze.
Maybe I've been missing something and others will show the way!