Hi cruiseeurope, welcome.
Sorry, I didn't go to this topic for a while so my reply is some late.
I think there's a real ship missing risk only if you absolutely want to visit Florence.
It's rather far from the usual ports of call (Civitavecchia, Genova). Livorno could be nearer, but I haven't ever heard of big cruise ships docking there.
Rome too is a bit far from the sea, but its real problem is that there are so many things to see you won't ever be ready to leave...