The Howard surname could very well be an error. The information was provided by Dwight D. Chapin's wife, Lula Kite. She probably never met any of his family and could easily have been mistaken about his mother's name. She got the birthplaces wrong - said both parents were born in Massachusetts, which was untrue.
As far as I know, Olive never went out to Wisconsin. Her mother, Mary Mitchell, and stepfather, Daniel Johnson, went out to Appleton in the 1870s; they were there for the 1875 Wisconsin state census. Daniel Johnson died in Appleton in 1878 and Mary Mitchell stayed on until at least 1880 with her son Daniel Johnson, Jr. and her oldest, widowed daughter, Isabella [Stanford] Allen. They all moved back to Boston at some point and Mary Mitchell died there in 1895.