Hi and congratulations, hope you'll have a brilliant time on your honeymoon.
I'm French too and I would advise to take the TGV (fast train) from Paris down to Lyon, and then maybe down further south. The trip to Lyon from Paris with TGV takes 2h10 minutes. It can be a bit expensive, but if you book your ticket in advance with SNCF, the railway company, you will pay less than if you got it on the spot. You book your ticket online, they give you a code, and once at the station you go to the counter to pay and they print your ticket (or you can do the same at a machine). It seems daunting but it's easy really, but I think you have to use a visa card.
I bet they also have a special "carte" (card) that, when purchased, entitles you to a good percentage off any rail travel in France for a number of days. There are also prices for people travelling together I think. Check out the SNCF website.
There is a TGV station in Paris's Charles de Gaulle airport, so an option would be to travel down South first straight from the airport, and then come up back up to Paris with stops on the way.
It's definitely worth your while to visit some other part of France than Paris, there are so many beautiful places it's hard to select one.
My own home town of Lyon is beautiful ;) Don't know when in Dec you're getting married, but on the 8th of December (!!!), there is a celebration called "La Fete des Lumieres", to honour the Virgin Mary who saved Lyon from the plague. Nearly everybody lights little candles that we line up on our windowsills or balconies for the night, and the town council illuminates the whole town too, churches, riverbanks, it's a fantastic night for a romantic stroll :) http://jtomei.files.wordpress.com/2007/12/793115-970987.jpg
http://www.catholique-chinois.fr/images/histoire/08dec.jpg