Looking for Descendants of David Ross Mckenzie Son of James L Mckenzie and Isabella Ross Mckenzie

I have been researching the children of my great-grandfather, David Ross McKenzie, and his first wife, Margaret E., who left him to run off and marry James M. Combes. They moved to Portland, OR, from Summerville, Union, Oregon, and took David and Margaret's two sons, Archie L. and Kenneth D. McKenzie, who both died in the early 1960s. I have been unable to find records on their daughter, Melba, who, according to David's obit, married a Mr. Summersett. There is a Melba Summersett, b. 1910, d. 2004, in Oregon, but I don't know if she is the right one. Does anyone recognize these three children? I am hoping to find their kids. Archie may have had a son named Dennis McKenzie with his wife, Alice (Hughes) McKenzie McKee. And Dennis may have had a child. I would love to have a McKenzie family reunion with them for my grandmother's benefit. Thanks in advance for any info!