Hi Naomi. We have been to the Med twice and can obviously only offer our perspective. We are 20 years older than you guys but are very active. We climbed thousands and thousand of steps and climbed many, many hills ..... great exercise, but very tiring because most of the streets and steps are cobblestone so you are not talking about smooth American surfaces.
Yes this is a VERY port intensive itinerary, so don't be surprised if you don't have much energy for evening activities onboard ship.
I can't help with Toulon but we have done Villefranche twice and absolutely loved the area. The best that we did was take a personal tour of Eze and St. Paul de Vence .... in fact I wouldn't go to the area and not go to these awesome medieval towns with lots of shops and restaurants and views to die for. The other cruise we stayed in Villefranche which is a little fishing town built on the side of the mountain. Lots of climbing and stairs other than the front street alongside the water. AS I said Villefranche area is unbelievably beautiful but you would have to travel out of the town to get the best benefit.
Pisa and Florence can both be done in one long day. Although the Leaning Tower was interesting, Florence was spectacular and there is so much to see and do there, depending on your preferences. We have also done this port twice - the second time we took a private tour of Tuscany and fell in love with Italy!!!!!!!
In Rome we took a private tour guide and saw so much, including the Vatican that by the end of the day my mind went on tilt .... you just can't explain the wonder of the history ... unbelievable. One thing I will say here is the difference between a private tour guide as opposed to going in a huge bus. We were able to get right up to everything in our car as opposed to the people who were at our dinner table that night who told us they took a ships excursion on a large bus and firstly were caught in a traffic jam on the intersate for 2 hours because of a fatal accident and the bus is not allowed to deviate from the set route (interstate) and secondly because of it's size it had to park on the outskirt of the city and everyone had quite a long walk to get to the sights. Just saying ........
Capri - I certainly wouldn't have said that Pompeii was any more strenuous than the rest of Europe. In fact I never felt it was strenuous at all. Hope that helps. For us visiting the Amalfi coast and the gorgeous little towns far superceded the time we spent in Pompeii. The Amafi is stunning .... we ate fresh figs off the trees, saw the biggest lemons I have EVER seen, bought lots of Italian Herbs (we love pasta) ate at the most amazing restaurants and drank lots of Limoncello!!!! Amazing memories!
To answer your question - yes your plan sounds very reasonable and doable. Enjoy all the planning .... that's the fun part!!!