Having done this sort of trip and hoping to do another this autumn (v. doubtful at the moment), I would say your itinerary seems rather rushed. My major suggestion is this - stay at Lake Como for a few days, park the car there, and take the train into Milan for the day. You won't want to drive into Milan. Even that lovely Porsche Macan will be a major hassle.

I recall that Il Sereno has had some terrible reviews on this Forum.