Thanks everyone!
The reason we have to backtrack is that we can't leave earlier than we already are (must leave after Easter) and we are meeting another couple who is traveling in from Cyprus. My buddy drives there so I don't think he will have trouble for the Amalfi Coast.
Florence for 4 nights is because one day we will be at Cinque Terre, one day a Tuscany Tour and that really only leaves one more day to do Florence which I think is enough time.