I think this is brilliant, for the record.
There's no obvious reason why this should be an issue that breaks down along partisan lines. (This being an election year, and the GOP being defined by nothing so much as reflexive opposition to anything and everything Obama does, it of course will.) Force the Republicans to argue in favor of deporting children. Cut off the "alternative DREAM" proposals being advanced by some slightly saner Republicans at the knees. Expose the fractures within the GOP on immigration in an election year.
The fact that it happens to be the right thing to do is almost gravy.