Q&A: Spring Break in Italy? Head to Rome

Our family is planning a trip to Italy for 7 to 10 days during spring break in March 2012. We have two teenage boys (ages 16 and 18). Our interest is more historical than religious. Could you suggest reasonable "must sees" while allowing for a little down time? And could you please suggest the best mode of travel? Carrie Bearse, Barnstable, Mass.