I´m going to give you the trick that I´m using.
I´m shooting a movie with my 7d(550d it´s almost the same in electronics) this days and it consist in a “all night, low light shooting”. The true to make your footage usable in post is to get the perfect exposure of your shot, do not under expose “NEVER” because of the limitation of the h.264 codec. The codec gets a little nasty when you try to bring up all the “under exposed image”, so try to get the perfect exposure, use the camera metering to guide you “DON´T THRUST ON YOUR EYE” whatching the LCD because they are very bright.
I´m shooting in ISO 1250, you may think “That´s a lot of gain” and yes it´s a lot of noise for the big screen BUT… Im geting a perfect exposure and that lets me work a lot with the footage. Also the trick is… “Do Noise Reduction”, I use the “DeNoise” plugin from “Re:vision FX” and it´s… Perfect. The footage looks perfect, the exposure is perfect and the final product looks perfect. The only problem is that Denoising takes time of render but thats an other thing.
Good luck.