Restaurant reservation

My girlfriend and i are traveling to Japan next week. My friend has told me about a romantic restaurant i would like to take my girlfriend to so i would like to email the restaurant to make the reservation. I have studied Japanese a little so i have a small idea but hope someone who is more of an expert than i could please help me. How do i say the following in Japanese..??
"I would like to make a reservation at your restaurant in a private room for 2 people on Monday September the 12th at 6pm"
Thanks in advance.

Marc,

How would you be able to entertain your girlfriend at a restaurant that can't even read your request in English? And why did you decide to have anonymous posters help you rather than your friend?

Anyway, just throw in
個室の蘭�をお願いします。
and write everything, including date and time, in English by yourself so that you can be responsible for what you wrote.

Uco,
I guess I should thank you for your answer despite it being negatively fringed.
To answer your questions, my friend was taken there when he visited Japan, he doesn't speak Japanese. He told me the menu is in Japanese and French which means we'll be ok.
Thanks for your answer and concerns.

Sorry, I didn't mean to sound negatively. Bon appetit.

Marc,

I am a Japanese, and as a standard Japanese, I am not good at English. When I was abroad, I was always worried about ordering in restaurants in English. However, it was always OK, and the restaurant people were very kind to me. I think they are providing their service and not to intend to blame me for my poor English.

Most of the managers of the restaurants in Japan are Japanese, and they might not be good at English, but they should be willing to satisfy their customers.

As UCO wrote, it is OK to write your mail in English. I think they can understand your reservation. You might better explain your situation in some detail: You are man escorting your girl friend, and want to be in a romantic atmosphere, etc.

And if you start your e-mail with some Japanese words, the manager will be pleased: most Japanese like to see foreign people using Japanese language.

For example,

こんにちは、来週から日本を旅行する嵐閧ﾌマークです。9月12日は蘭�できるでしょうか？

and end up with

お返事よろしくお願いします。

Enjoy your trip to Japan!

And of course, in Marc's case, 個室 is more important than the date and time.

Here is a lovely, romantic restaurant we went to last May. They have a lunch Bento that is a great bargain - and very good.
http://dickh.zenfolio.com/p946680586

I forgot to mention, no reservation needed and all the rooms are like in the photos.

Thanks for all the answers.
As i said, i can speak Japanese half decently and have some idea with the writing, but needed some help to make it perfect.
I appreciate the help and advice and have emailed the restaurant successfully now.