You take the local Malpensa Express bus to Milano Centrale station. They run often and your luggage will fit underneath.
I would buy tickets then since you cannot be sure of your timing. The trip only takes 2:35 and the tickets cost 43E or 31E---for that difference I would go first class.

There are now train options from Malpensa that eliminate the need to take the shuttle bus from the airport to Milano Centrale.

At the link below, find the connections that are possible in relation to your flight arrival. You'll be travelling from "Malpensa Aeroporto" and "Venice S.L." and you can buy the entire train ticket at the airport. Taking train-train rather than bus-train means you'll already have your ticket, and all you need to do is move from the arriving train's platform (binario in Italia) to the departing train's platform.

http://www.fsitaliane.it/homepage_en.html

Hi ediemay, I have recently been to Italy on a Globus tour that covered pretty much ALL of the places you mentioned in your original post. It is the Globus "Best Of Italy" tour and I have given a very detailed report of it in my trip report: http://www.fodors.com/community/euro...the-report.cfm . It might be worth looking into if you can't pull everything together in time. I wish you all the best with your trip!

Irishwhistler90 ,read and enjoyed your report and learned a lot from, but we are going to try to travel independently.
Bob and Jean thanks for your prompt responses. It sounds great if we ca go direcrly to the train at the airport. Will definitely look into that option.

You'll be travelling from "Malpensa Aeroporto" and "Venice S.L." and you can buy the entire train ticket at the airport. Taking train-train rather than bus-train means you'll already have your ticket, and all you need to do is move from the arriving train's platform (binario in Italia) to the departing train's platform. >>

and don't forget to validate your tickets in those funny yellow machines on the platform before you board the train!