Joseph Ducharme and Rose Nolin were indeed married on Feb, 11, 1879, as stated. According to my files, they had a son named Jean (John, in French), born around 1890. This could be the John you are looking for.
However, I find no Frederick, Emma or William among the other children of Joseph and Rose. The children that I have in my files are:
*Daniel-David, born March 16, 1880 *Zacharie, born Aug 12, 1881 *Melanie, born Aug 06, 1883 *Moise, born 1884 *Alfred, born Jul 28, 1885 (could be known as Frederick) *Nancy, born 1888 *Jean (John), born 1890) *Raymond, born 1892 *Alice, born July 14, 1894 *Elie-Raphale, born Aug 14, 1896.
This list comes from the notes of Father J.O. Plourde, a missionary in Manitoba at that time.