Thanks very much to all who responded for the information and suggestions; it is sincerely appreciated.
I suspected that 3 weeks may be pushing it and extending to 4 weeks would not be entirely out of the question. We would like to do both Oregon and California if possible. I have no doubt we will be back to the Oregon coast, but the years seem to tick by quickly and as a result who knows when that will be.
Avoiding SF may be logical; it will be disappointing to my wife and myself but likely makes the most sense.
Thanks again and please keep the suggestions coming!