External microphone for easy video shooting

Dear all,

I want to buy external microphone for my 7D to improve sound quality of the videos.

I am not intending to shoot concerts, or anything, where excellent sound is vital, it will be more less about family gatherings and so.

As I have no knowledge about audio/video recording, I need your advise, on which features the microphone should have and which, according to what I will be shooting I don’t need.

Shooting video will be just marginal compared to shooting photos (so I don’t want to spend more $ than necessary), I will be using Canon EF 70-200mm f/2.8L IS II and EF-S 15-85mm f/3.5-5.6 IS USM lenses.

I prefer to buy the microphone through http://www.bhphotovideo.com/

Thank you for your thoughts!

Tony