I'm going to be writing an addendum as well, but I'm taking a slightly different slant. I was very involved in school, and worked quite a bit as well, but I am just giving those issues a cursory discussion. Instead, I am trying to point to my WE as being a better indicator of 1L performance than grades.
I feel that I accomplished enough in school to overshadow a low GPA, but so does everyone else with a low GPA. And I'm afraid that the standard I worked, I had a hard major, I had to grow up thing is quite hackneyed. I just don't see how that would differentiate me from other applicants in similar situations. Not sure if WE focused addendum is that much more unique, but I feel that, in my case, it carries more weight. Just some food for thought. (I actually hate that phrase).