Yes, the Beachtek DXA-2s will work fine with the 7D. The only issue you will have will be the AGC (auto gain control) in the 7D which will regulate the input based on the levels. When the sound is loud, it brings the volume down, when the sound is quiet, it brings it up. So... when someone starts a sentence after a pause, their first syllable can be really loud, then the AGC brings the volume down to an acceptable level... which can be an issue.

The controls on the DXA-2a will not correct this.

One thing you can do, if you're interested in taking it to the next level, is trading your unit in to Beachtek and getting their new model, the DXA-5D. Beachtek is pretty cool about this stuff and will give you a $100 credit with your trade-in towards another model.

The DXA-5D emits a constant tone that is below audible range (the camera can hear it, but we can't) that regulates the AGC and doesn't allow it to spike or dip. In practice it works very well from what I've read.

Or you could, of course, stick with what you've got... it will work... you'll just have to get used to the levels changing as your source changes. Depending on what you're recording, this may not be too much of an issue.

from what I understand in the specs of the Beachteck and from what I remember of the 7D when I tried it, yes.