Welcome aboard, Reinclaire!
How exciting to hear that you'll be visiting the beautiful Mediterranean in 2016. My family and I sailed that voyage a few years ago when my kids were about the same age as your daughter (about 5 and 7 years old), and we had a spectacular time. The Mediterranean voyage visits amazing ports of call -- and you get to learn so much! When the kids were at the Oceaneer Club, they even learned a few things about the places that we were visiting -- the Youth Counselors are great! They even practiced some local lingo with the kids. :-)
We quickly found out that visiting Europe does indeed entail a lot of walking... I don't think there's anything around that. So, make sure that everyone in the family wears comfortable walking shoes. Most of the Port Adventures will be labeled as mild, moderate or active types of activities. The excursions usually last most of the day, so you can be guaranteed that the little ones will be very tired at the end of each day.
Pisa was a must-see for us while we were at La Spezia. The significance of reading it in books, made it worthwhile for us to visit the Leaning Tower of Pisa, and see it with our own eyes. We had great pictures!
While we were at Naples, we did an action packed adventure touring
Pompeii, Sorrento & Capri. It was fascinating, but we did take a lot of stops to rest. We actually ended up leaving our kids onboard when we visited Rome. The adults got to explore Rome and the Vatican, while our kids enjoyed the activities onboard the ship's Oceaneer Club, for the day. It's wonderful that parents have this option when sailing with Disney!
I hope this help, Reinclaire!
~ Dolly