I'd definitely go with a French theme. You could have an elegant dinner - white table cloth, lots of candles, fine food, etc. Think of something these Parisians would have before going to the opera. However, I think I would prefer appetizers and desert while watching the movie. Again, go with a French theme. You could have slices of baguette and brie or other cheeses. Have some wine. And don't forget to run to the store for some fancy French-like pastries.

Since it is close to Mardi-Gras, you will likely be able to find decorated masks at a party store. Craft stores might have undecorated ones. You could use the masks just as decoration, or decorate them for an activity, or have some kind of creative mask competition.

It sounds like fun!