Thanks everyone! Great tips.
I've happily noticed how many things... trains and sites ... are free for 18 and under. It's nice to not have to multiply my per person budget for the trip by seven in all things. If only airfare was so family friendly...
Having the oldest keep the kids is a great idea. He actually proposed that to us, to keep the kids a couple of nights over the trip so we'd get our date night. That is quite nice as we'll be in Naples for my wife's birthday.
The meeting place and emergency address/money is a great idea too. I hadn't thought about letting the older ones split off on their own at all.
I am a little concerned about how mealtime will go down. A couple of our kids are pretty vanilla in their food choices, but we're trying to get them to experiment. Thankfully, any form of pasta with pesto has typically gone over well at home so the green stuff shouldn't be an issue. I also remember a lot of the places being pretty small so I'm not sure if we'll run into issues with the size of our family wanting to take over an Osteria...
One thing we've talked about with them is how the trip is not just what's at point A or at point B but exploring everything in between as we'll be on foot a lot. We've told them there may be days where our plan for a few hours is to go find a particular gelato shop, but see what we can discover en route. Hoping to avoid too much of the "are we there yet" syndrome. Is a stroller worthwhile for the 4 yr old? Typically we just throw her up on shoulders/back and keep on. And I agree that flexibility is pretty critical while out and about.
We'll be hitting Ischia, Naples, Rome, Florence, and Venice over three weeks. Florence was the shortest stay and the kids opted to skip a day trip to Pisa/Lucca from there in order to have more time in Florence itself. They ruled out the Vatican, are excited for the Colosseum, and I think would be content with pizza, panini, and gelato as our regimen for the duration.
I appreciate all the info again. Looking forward to other tips as they come in.