Hello,
I am a Dueck by birth. I know that a Wilhelm and Anna which are relatives of mine (great grandparents) are buried in the Mennonite cemetery on Willow Creek Rd. in Paso Robles, California.
As for Dyck spelling that is a different family strain than the Dueck. My grandmother's maiden name as Dyck, She married John Dueck thus making her Helen Dyck Dueck.
FYI- in my family both Dyck and Dueck were essentially pronounced the same way.