I'm in a similar situation. I am 33 and in my 1L year as a career change after being a corrections officer. My grades, overall, were ok (some great, some average), but I have had a few interviews in the Philly/NJ/Del area and have a few more set up in the next few weeks.
Based solely on my experience over the past few weeks, I have found that every interviewer (except one, who had no interest in anything I had to say) wanted to talk about working in a jail and how I was able to go to undergrad full-time, make dean's list throughout and still work 50 hours per week in a jail.
Bottom line is this...you should be fine either way you go. You're background makes you interesting and, at the end of the day, most summer employers will want to talk to someone with a background that is a bit different than the usual 23-25 year old who went to law school straight from undergrad with no life experience. As long as your grades are not in the toilet, no one will care. I've had a total of 7 interviews and was asked about my grades ONCE. Again, this is just my experience and, to be fair, all of these interviews were with government agencies and public interest organizations, but still only one out of seven asked me about my grades. For you, as long as you get the interview, you'll probably be fine.
Now, how to get the interview. I can only tell you what's been working for me. I have been on the phone since finals ended last fall, calling different firms/gov't offices/public interest groups, and asking if I can send a resume. What has happened is that they ask me a bit about myself (Name, where I go to school). Then they ask me to send a resume or they tell me that they've hired enough summer interns this year. If they say "send me a resume" then you're sending your resume to someone who is looking for YOUR resume. I think that makes it a little bit less likely that your resume will end up in the circular file. Also, utilize your career services office. When I got to my school, all the 2Ls and 3Ls bitched about how bad career services was. I have been riding their ass like the Lone Ranger and I have to say that they've been very helpful. Basically, take advantage of all of your school's resources and you should be fine.