There were twenty men named Earl DUNHAM b. ca. 1899 - 1909 on the 1930 census database, including three b. 1900 - 1904 just in Oklahoma. I found no Earl D. DUNHAM with a Bonnie. However, there was a Violet C. DUNHAM of Shawnee Co., KS (no Earl with her). There was a Bonnie M. ROBERTS, b. ca. 1909, of Seminole Co., OK. There were 29 named Bonnie ROBERTS b. ca. 1900 - 1920, in 1930, but that was the only Bonnie M. in the area.
The 1900 Census of Sedgwick Co. is online (free) through USGenWeb > KS > Sedgwick County, but Wichita takes up several pages, and I have dial-up Internet, so I didn't search it to verify your DUNHAM names and ages at that time. El Dorado is in Butler County, just east of Sedgwick, but I couldn't find a search engine for Butler County. Marriages there appear to be available through Ancestry.com membership.
Where do you think your Earl was in 1930, the last available census?