You are in for a treat. We did Venice, Tuscany & the Almalfi Coast in Feb. of 2011. Had a fantastic time. Suggestions: In Venice you probably will have free time. Just start walking and see everything you can possibily see, what does it matter if you get a little lost? You won't have a strict time schedule and unless you jump in the water and swim away you will still be in Venice. I would highly recommend going to the little island of Burano, it is so colorful and fun to see.
We did most of the optional trips and were pleased that we did.
I had done some research before we left home and while we were in Tuscany we took a local bus to Montepulciano and had a fantastic day. While on the Almalfi Coast part we took a local train and went to Herculaneum. You ask, how do I know if I'm interested in these places, well guess what? I have a travel blog and it's complete with a little info and lots of pictures.
I will tell you that we have been to a lot of places, but the bus ride along the Almalfi Coast is perhaps one of the most beautiful days of my life. If you have any questions, please feel free to ask.
Take a look at my travel blog, the trips are listed on the left hand side of the opening page. www.thefarmersmeanderings.wordpress.com