Carole,
Yes you can book a 3rd person on Crystal. All Pentouse Suites will do 3 people.
Inside, Outside, Reg Balcony will do 3. I found that the Harmony is doing 2 10 day voyages early...June 14 2002 Seward to Vancouver and June 24 Vancouver to San Francisco. After that she is doing 12 day San Francisco round trip.
Michael