You will absolutely love spending time cruising the Mediterranean this summer, Jennifer!
This itinerary is action packed and since you sound like the adventurous type, you'll surely have tons of activities and port excursions that you can check out as you prepare for your voyage.
My family had an amazing adventure out in Europe on this cruise -- there's just so much to see and do. Depending on your interests, you'll have something spike your interest while visiting these culture-rich ports of call. I answered a
family-based excursion inquiry recently, just in case you'd like to see that posting too. In addition to the suggestions there, you'll definitely want to play around with the Port Adventures listing online. There are different levels of activities to choose from that you and your sister might be most inclined to do.
Naples offers a nice adventure as you drive through the
Amalfi Coast and see the ruins of Pompeii. It's a full day event and also includes lunch. La Spezia seems to just scream for you to climb the Leaning Tower of Pisa. If you'd like to do more sightseeing in Villefranche, there's also an adult-only excursion that visits
Nice and Monaco.
Prepare for the warm weather and lots of walking while out in the Med, Jennifer. You're in for such an amazing trip with your sister - have a great time!
Happy planning,
~ Dolly