Amy,
There are only ~ 400 practicing gyn oncologists in the USA.
Odds are that if you go to a reputable University teaching institution, and find a BOARD CERTIFIED GYN ONCOLOGIST you would probably, but not absolutely, be fine.
Most States in the country have websites where you can check a specific physician's credentials to see if they have had any malpractice judgments filed against them. If you find a gyn oncologist in Seattle, this is the first thing you should pursue: check out their track record.
If you think of traveling out of state and MN is not far from Washington, Mayo Clinic is one of the finest institutions in the country for all cancer surgery, bar none.
Good luck to your family.