Glen first married a Margaret Fiore on April 6, 1940 in Idaho Falls, Bonneville Co., ID.
Source: Idaho Marriages 1842-1996. Record can be found in the marriage book at the Bonneville County Courthouse in Vol. 6, pg. 446.
Since he was married after the 1930 Census the only way to find information about his children is to request copies of Margaret, Jane and Glen's obituaries.
Since Glenn died in Gallatin Co., I'd contact the Montana State Genealogical Society volunteer. Her contact info can be found at rootsweb.ancestry.com/~mtmsgs/msgs_researchers.htm .
If that researcher doesn't work out, there is another at Random Acts Genealogical Kindness. Go to raogk.org
Click on Montana
Scroll down to Gallatin Co. & choose Jane. Successful Searching!