Vigorously.

"Ooooh, Mother," groaned Joffrey, as Cersei energetically pleasured him, her mouth bobbing back and forth over his entire length. The tent filled with the smackings and gurgles of the Queen's blowjob. Glancing over at the Starks, Joffrey noted that Sansa and Arya were staring at the debauchery occurring before them with undisguised fascination, eyes slightly glazed. Sansa gulped nervously, while Arya made a low, quiet moan.

Releasing his cock from her mouth, Cersei gave it a long, sloppy lick, then turned to regard the sisters. "Well? Out of those dresses! If you will not pleasure the King yourselves, you should at least let him enjoy looking at you." The pair nodded quickly at this, and then went to work, slipping out of their garments to reveal their nude young bodies to Joffrey's appreciative gaze. As they did so, Cersei went back to work on her son's dick, swallowing and licking it with relish. She paused to regard the sisters once they were fully undressed, smiling wickedly at the pair. "Very nice," she murmured, hand stroking Joffrey's hardness. "I can understand why you've found them such... enjoyable company." She gave a brisk nod. "Well, come here. Show me if you've learned anything from my little... demonstration." Sansa and Arya nodded again, and crept forward on their knees.