There's a lot of questions surrounding the Deferred Action law ( otherwise known as the DREAMERS act) these days. Will USCIS use the information obtained in the applications against the applicant or even his/her family?
All I've learned about this question points to the fact that no, USCIS will not use it for removing others in your family, and although there is not guarantee as such, my advice is this: You are taking a risk b being illegal everyday, this application poses a risk much smaller and has many more benefits. So I say, of course, those that are eligible should apply. I am charging $450 for these applications, although I know this is a ridiculously low fee for an attorney. Being the child of an immigrant family makes me sympathetic I guess.