I found Fred and Hazel listed in the 1920 in Deschutes County, Sisters Precinct Page 4a
McKinney, Fred L. head/male/white/age 32/married/born Oregon/father NC/mother NC/mechanic in a garage McKinney, Hazel B. wife female/white/age 32/married/born Iowa/father Indiana/mother IL McKinney, Carrie I dau/female/white/age 10/single/born OR McKinney, Kathryn D. dau/female/white/age 3(?)/born OR
Listed right above them on the census was
McKinney, Moses head/male/white/age 58/married/NC/NC/NC/laborer/Railroad McKinney, Ida wife/female/white/age 53/born OR/Iowa/Iowa Mckinney, Herbert son/male/white/age 26/single/OR laborer-streets McKinney, Lillian dau/female/white/age 20(?)/OR
I couldn't find the family in 1930-there were two Fred's listed but neither matched. Couldn't find Moses and his family either. Then I checked in the Oregon Historical records and found an interesting for Fred and Herbert.
Frederick Lester Mckinney born Aug 29, 1887 Evidence/Gilliam County Herbert S. McKinney born October 2, 1893 Evidence/Gilliam County
You may want to check those records out for yourself. I did find Fred and Hazel listed in the Oregon Death for the dates you listed.
Hope this helps. Let me know if you neeed more help.