Brian of nzolivers.com generated the following search results of official BDM Historical Records showing children born in New Zealand to Louisa and Samuel:
1875/9161 Gates, Ernest Louis
1876/11311 Gates, Frank
1878/14616 Gates, William James
1880/5341 Gates, George
1881/11799 Gates, Ada
1884/6932 Gates, Gertrude Jane

Name and year of birth from above BDM Historical Record.

Date and place of marriage from research file03 in June 2017.

Date of death of 2 Jan 1942 (Unknown age on grave), from billiongraves.com website for Greytown Cemetery.

William James Gates, Baker, of Greytown listed in the New Zealand Army WWI Reserve Rolls, 1916-1917, 1st Division Wairarapa, ex Ancestry.com.

From the Greytown section of the 1913 Wise’s New Zealand Post Office Directory, City & Area Directories, 1866-1954:
Gates, Wm. [William], settler

From the 1916 Wise’s New Zealand Post Office Directory, Greytown section:
Gates, Wm. [William], baker

From the 1923 Wise’s New Zealand Post Office Directory, Greytown section:
Gates, Wm. [William], baker

From the 1926 Wise’s New Zealand Post Office Directory, Greytown section:
Gates, Wm. [William], baker

From the 1930 Wise’s New Zealand Post Office Directory, Greytown section:
Gates, Wm. [William], baker

From the 1933, 1936, and 1938 Wise’s New Zealand Post Office Directories, Greytown section:
Gates, Wm. [William], baker