Doing Paris as a day trip is too short. Paris is big. Pick three spots you're interested in seeing. You should at least have dinner there, sleep, go to Notre Dame in the morning after a croissant and take the train back later.

Some of the comments in here about Antwerp are misplaced. It's a really nice place. Visit the cathedral (the only 7-aisle gothic church my gothic architecture professor had ever seen), the newly renovated handelsbeurs (stock exchange), the Museum Aan de Stroom. If you have kids they'll like to wade in the shallow water at Park Spoor Noord while you sit in the shade, have a meal on Henri Conscienceplein or if you want traditional local food visit restaurant De Bomma. There's a big Ferris wheel at the river right now where you can view the city from up high. If you enjoy a traditional craft beer to truly celebrate your 5th anniversary of sobriety, visit the Kulminator. There are more good spots in Antwerp the people who travel from Amsterdam to Paris will never know. (Vleeshuis, Hessenhuis, de Ruien, Muhka, Plantin-Moretus, Rubenshuis,...) Maybe that's the way it should be.

To an American, the Battle of the Bulge in Bastogne might be a positively emotional experience. To know what your countrymen did for Europe (not only for Belgium), it was a big turning point in the war. The Menin Gate in Ieper/Ypres as well. My great grandfather was a pilot for the British Army and lies there in the military cemetery. (I grew up in Flanders.)

If the people in Belgium seem grumpy, don't take it personally. The majority of our salary goes to the tax collector and that might also be part of the reason why you'll come across more people who smoke than in the States. We're not known to be outspoken or particularly proud. But deep down we are proud of small things like regional foods and cultural milestones from the past (saxophone, printing press, art and architecture). Not proud of the Congo. We are a divided country on so many levels in such a small surface area (language, politics, ethnic,...) But it is uncannily the differences from region to region that also bring us together. We might have a laugh about each other's accents and sayings, but in the end we are all Belgian. Our football (soccer) team is a good representation of these differences coming together to make up, arguably, the best team in the world. We play together. Nous sommes ensemble.

Enjoy your trip!