I am not an expert by any means, but I have been around a little and had my wedding in Italy.
Had a friend get engaged on a gondola in Venice. Pretty cheesy, but she will probably say yes, because she can't go anywhere.
Also, there is a villa in Tuscany that is a fantastic get away.
http://www.villaschiatti.it/ My wife and I stayed there when we got married. Patrizia, who runs the place, is very helpful.
If there, I would reccomend a proposal at the restaurant Da Delfina in Artimino. The food is fantastic with a cozy atmosphere. There is a patio outside that looks out on the valley with an awesome Medici villa across the way. End of the semester it will probably be a bit chilly at night. You can eat, then go outside to look at the villa. Give her your jacket. Propose. she-bang. Let Carlo at the restaurant know and he will make it special. He is a romantic at heart. Faxing the restaurant is the best way to get in touch with him. You can also get a room at the Medici Villa to cap it all off. Something you would not forget.
Remember that this is only your first trip to europe. If you try to do it all, you will end up not really doing anything.
I also have to say that there are many great places in the netherlands. I am sure some great advice from natives on here can help. Contrary to american beliefs, there is a lot more in the netherlands (and amsterdam for that matter) than pot and brothels. Nothing wrong with those, but even amsterdam has a few lazily charming districts.
Paris has a reputation as a romantic city for a reason. If everything falls in place, it is fantastic. If you approach the city as if it is your adversary or your playground, you might have some issues. Some of my fondest memories are from an October in Paris. The leaves were starting to fall. It was pretty cool.
Most places in europe are a short distance from an appropriate setting. Like I said, I'm not an expert, but feel free to hit me up on ICQ and I can give you my unsubstantiated opinions.
