We want to take a rental car to Ishcia and/or Procida. Would it be better to take the car with us or leave it at one of the parking lots at the Naples ferry? If the answer is leave in Naples, which parking facility is best?
Many rental companies prohibit ferry usage to islands.
No rental cars on islands period. You don't need one on Procida!!
If these are day trips absolutely no car needed. Take taxis on Ischia. The is a round the isle boat trip that stops at 4 major towns.
Staying on Ischia? Try Baldisteri in port as you exit ferry one block up on left for Ischia rental. You really need a car if staying more than 2 nights as bus service is horrible. Easy driving but tough parking in most areas, be prepared to pay.