Sonics guard Ruben Patterson is expected to be charged today with attacking his children's nanny at his Bellevue home last fall.  At the time of the attack, Patterson faced a felony assault charge in Cleveland, where he was accused with three friends of beating a man outside a nightclub last June.  Patterson is expected to enter a modified guilty plea Friday at his arraignment to attempted third-degree rape, which could help him avoid a jail term, law enforcement sources said yesterday. Patterson is expected to opt out of his contract this summer for free agency.