There are two fabulous ones to consider:
Alpenrose Dairy in Beaverton has one of the largest easter egg hunts in the Portland area and it is always lots of fun. They have a special 'hunt' for moms too that usually involves a pair of diamond earrings from a local jeweler also that is hysterical to watch/participate in.
Oregon Zoo in Portland also has a great easter egg hunt.. they actually do several all day long, and it is a fun time!
Last but not least, check with your local parks and rec department... most cities/suburbs in the portland area have one sponsored by the park department.