If you go to the search engine for this forum and type in pronunciation into it, you will find two pages of the way people pronounce Cheney. including mine from 2002. I believe then, as now, that however a Cheney pronouces his/her name is the correct way. There is clearly no one way. I myself pronounce it CHEE-knee. I decend from John of Roxbury. Lynn Cheney was once asked on tv (I was watching and listening intently) how to pronounce her last name. She very clearly said CHEE-knee.
Slightly off topic, regarding the spelling, I find it interesting though that my gg-grandfather Alonzo Edward Cheney, on his gravestone in Nebraska, has it spelled Cheeney. He clearly lived his adult life, after enlisting in the Civil War, spelling it that way. His father didnt, as per Wisconsin newspapers and his California Death infomation. He spelled it Cheney as did Alonzos siblings. Alonzos sons, Charles Chauncey and Ernest Elmer spelled it Cheney their whole adult lives. I often wondered if he was running/hiding from something and changed it or just got tired of correcting the pronunciation. Based on 10 years of research on him, I have a strong suspicion it was not the latter. Genealogy is my lifes passion and I tend to babble about ALL aspects of it. Sorry.