“Obama” can pardon illegals for any and all crimes they have committed (unclear if he can do this as a class, however - he might have to sign 12 million papers).
He cannot grant them citizenship and he cannot issue green cards without legislation.
The DACA recipients have their status renewed every two years. Does anyone think that the GOP will try to revoke that status? In fact, Cantor was preparing the GOP verison of a Dreamer amnesty. There are more than 50 Reps in the House who support amnesty. The only disagreement they have with Obama is process, not the objective.