I'm not saying this as a bad thing, but I do believe that parents will try and exploit the DREAM act. The simple reason is that it is human nature to try and get an upper hand through the easiest way possible. So what is easier than having sex and anchoring to a child?
There are people who go to frightening extremes to come to this country, and some of them do it repeatedly. Obviously, they really want to be here. If you give them a path to citizenship that allows them to stay (and they know about it), then yes, at least some portion of them will take advantage of it. I'm not sure that's such a bad thing. If we are unwilling, for some reason, to allow open immigration, then we leave these people little alternative.
This is because the law has rules in place to prevent exploitation. The law requires the person to graduate highschool and meet multiple other checks to gain their citizenship. If they do this, then it does not matter that they are citizens because they have worked to improve themselves and prove themselves as americans in order to gain citizenship.