Cable Chief Tries to Bring Cool Into Disney Children's TV
Geraldine Laybourne is credited with building Nickelodeon into $300-million-a-year money-maker by being plugged into what children really want to see on television; she brings that expertise to her new job, president of Disney/ABC Cable Networks, which includes broadcast network's children's programming; Laybourne will oversee Disney Channel's new president, Anne Sweeney, who is working to give channel sharper identity and bit more spice while still keeping family entertainment mandate; cable television has attracted so many children that advertisers spent almost as much on cable last year as they did on four broadcast networks; chart; drawing (M)