Realistic Budget?

Do you have transportation from one city to another also set up? (rental car, train, etc)

In addition to the transportation Robyn mentioned, you will spend a few euros here-and-there for admissions. Some churches are free, some ask for a donation, can be 2-6 euros. Do try to see the Frari Church in Venice. It is fantastic; 3 euros per person. You may need to do laundry once or twice, which can run 20-25 euros, even in a self-service laundry. I doubt that two of you will spend 100 euros per day every day on meals (unless you drink Coke in large quantities!), so you have some wiggle room in your budget. Some days will be much lower, a few a little higher unless you are into "fine dining" at every meal. We spent an average of less than 80 euros per day, and we had wine every night. Always nice to budget more and spend less. :-)

You could easily get by on less than 100 euro a day for food unless, as Robyn said, you're into fine dining the whole trip.
I think also, for the most part and depending on what kind of souvenirs you plan on getting, you could spend less than that. Venice, yeah you could easily spend that on one mask. Don't go for the souvenir stands around the main attractions. For example we saw the same exact things in little shops around the corner from the Trevi fountain for almost half the price at the stands near the fountain. The gondola ride you can haggle down. We got it for 60 euro.

Thanks for the replies. I have figured out rail transportation, but I am keeping it seperate from this budget. It's good to know that we are estimated high for food... I figured we were... we are hoping to have many a picnic lunch, then some nice dinners.
My husband and I are not 'museum' people, although we are excited to see many of the main areas. It's good to have some spare change while wandering though, you never know where you will find yourself :)

I wouldn't say that you are budgeting high for meals. We tend to spend more than most people on food, primarily because my husband loves Italian wine, and because I love to try all sorts of local food. We usually eat at a couple of splurge restaurants, many mid-priced places, and usually have something like pizza for lunch. Add on at least several gelatos a day (!), and one or two stops at cafes for wine or coffee, and you've made a dent in your daily food budget with just that kind of stuff. On the other hand, I doubt that I've spent 120 Euros on souvenirs on an entire trip, ever. Obviously, souvenirs are a personal choice. (Maybe food is my souvenir!) Also, I know lots of people buy the vaporetto pass in Venice, but we've been to Venice five or so times, and have never bought it. We'll ride the vaporetto once or twice, and all the rest of the visit, we walk.