"As one of the Traitor Legions, the Emperor's Children invaded Earth, but took little part in the fighting around the Imperial Palace. Simple pleasures had given way to complex debaucheries. While their allies fought and died the Emperor's Children slaughtered more than a million people and rendered them down to create endless varieties of drugs and stimulants. Countless thousands more died to give the Legionnaires more direct, if cruder, enjoyment."
Realms of Chaos: Slaves to Darkness, p. 263
So no, the Noise Marines are just one aspect of the Emperor's Children, but the above is not exactly so easy or acceptable to show and portray to little kids.
Slaanesh is the god of excess and decadence in all things, not just sex and rock'n'roll. That is why Khorne hates Slaanesh, because Slaanesh reduces Khorne's reason for being (i.e. killing) into just one of many pleasures.