Shouldn't be a hard choice. The kid should choose to be with his mother if he was any kind of a son. Unless he was being abused, of course.
Anchor babies, though citizens by federal law, is contingent on the interpretation of the 14th amendment. There is still debate going on concerning the 'subject to the jurisdiction' clause. The mother, according to some, (and I agree) cannot be subject to federal jurisdiction until she becomes a citizen as provided by law. Therefore, her child should not be eligible for citizenship either. IMO.
I agree, this anchor baby stuff is ridiculous. I actually think repealing that interpretation would slow down illegal immigration considerably as women would have less reason to want to come over the border. Furthermore, the judges would have less reason to prohibit sending them back. Now, you get the anchor baby and likely as not you get the parent(s) who get to stay despite the fact that their first act upon entering the US was to break Federal law.