The certification itself isn't worth it if that's what you're going for, IMO. Yeah, being CPR/First-aid certified is kind of cool I guess, but don't do it to put it on the resume. Of course, being a lg is a pretty chill summer job. If you just need a job to make $, then go for it. But, if you're doing this in hopes of adding to your qualifications for med school admission, I think being CNA-certified or something else (perhaps EMT if you have time) will be better because you're able to log clinical-related experience as a result, which does count.
So, to answer your question, it doesn't look bad, but it doesn't count for much, if anything.