Amalfi Coast in December for Honeymoon

It will be cold (cold is relative...) and there will be limited ferry service that time of year. Most hotels and restaurants will also be closed starting in November through March.

I would suggest Rome and Florence with your timeframe. You can take day trips from Florence into the Tuscan countryside. Rome and Florence will have some lights and decorations, but not like Lucerne or Munich.

Thank you so much for your quick reply.

So can we add Lake Como to our Itinerary with Rome?

Lake Como is not a good location for winter if you want beaches and open shops. It's even farther north of the Amalfi Coast so will be even colder, and many businesses will be closed.

You have time for two stops. With respect to Rome and Florence, you would fly to Rome round trip; head directly to Florence by train [about 2.5 hours] with a stay in Rome at the end [train trip 1.5 hours back to Rome]. Rome and Naples you would do the same thing. From Naples, Sorrento and Capri would be possible day trips.

It is not clear whether your dates include arrival and departure. If the 20th is the departure date, you actually have 7 usable days. Even if you arrive early on the 12th, you will be tired and jet-lagged. It is a big mistake to try to cram too much into a short trip. Additionally, the Amalfi Coast is best when you can count on good weather.
My advice is to keep your itinerary to Rome and Florence, as someone already suggested, with, perhaps, a day trip from one or both. A half-day walking tour, with a knowledgeable guide in each city, would be an excellent investment. Rome especially, is huge and packed with important historic, architectural and artistic sights. Take some time to wander a bit, people-watch, sit on a piazza drinking coffee or eating gelato.
I also recommend that you purchase a good guidebook so that you get a sense of what you may want to see and do.

Thank you everyone for sparing time and valuable suggestions.
I will arrive on 12th December and depart on 20th.

I wish to spend 13th and 14th in Lake Como;
15& 16th in Cinque Terre and 17, 18 and 19 in Rome.
I feel Florence would give us the same vibes as Rome has to offer. Wish to include Lake Como just to make my honeymoon more romantic.

Here are the average December temperatures for the Amalfi Coast (58-48). Lake Como (49-41).
Cinque Terre (49-41).

As suggested above, Florence and Rome which have a totally different atmosphere, would be the most attractive at this time of year with many Christmas related festivals. If the weather is inclement, there are still many things to do or see. Both avail themselves to good day trips.

Sorrento, is decked out for the season with most restaurants open. It has ferry access to Capri if the seas are not too rough.

I do not recommend Lake Como in December. It will be too cool and much will be closed. I wonder if Venice might have some of the Romance you are looking for. It is a magical place.

I love Florence, but unless one of you is an Art History major, Rome is more romantic, and has a wider variety of things to do in winter. Have you considered southern Spain, maybe Granada and one Ballearic Island? Still risking cool swimming weather except maybe un-romantic Malaga.

I also would expect the Cinque Terre towns to be mostly shut down unless they have Christmas markets (?). If the weather's poor (even dull gray days without rain), it won't be charming. Frankly you are looking at places that attract tourists because they are scenic/romantic in spring through fall. Winter's a completely different atmosphere.

I think Venice is very romantic. It's a wonderful place to start your trip, then take the train to Rome. If you can't get a flight into Venice, consider flying into Milan and then taking the train to Venice.