Marcel Cerdan Sampson, 33, allegedly tried to recruit fellow members of the Black Gangster Disciples to threaten the families of the children, SeattlePI.com reported.
Sampson was convicted in 2007 of immoral communication with a juvenile. He was released in April 2008.
Investigators say he sexually assaulted five children ages 4 to 13, all of whom he knew. He has been charged with first-degree child molestation and first-degree child rape.
Senior Deputy Prosecutor Carol Spoor has asked that he be held without bail. She argues he faces a life sentence if he is convicted because of his criminal record and the serious charges he now faces.