Hi Mimi, regarding Belle, she doesn't appear in the Censuses after 1910 in Elberton. I'd assume she married and would contact the Whitman County Court House to see if they will search through the records or when the records were sent to State Archives.
Also the Whitman County Genealogical Society, www.rootsweb.com/~wawcgs/res.htm does research for a reasonable fee.
Regarding William, the best way to find out about his life after 1930 is to get a copy of his obituary. Random Acts of Genealogical Kindness, www.raogk.org, choose Oregon, choose Multnomah County has a volunteer who will look up obituaries. If that doesn't work, re-post and I can give you two more places to look.
Regarding Benjamin, he filled out his World War I Draft Reg. card June 5, 1917. He was living in Farmington, WA. Born 19 Aug 1888, Elberton, WA. Farmer, self-employed, Farmington. He had a wife & two children but didn't claim an exemption from the War. He was tall, slender with Gray eyes and brown hair.
A Benjamin Harrison Bishop b. 19 Aug 1888, lived in Farmington, WA, County Benewah, ID. Source: WWI Civilian Draft Registration.
A Benjamin Harrison Bishop b. 19 Aug 1888, Elberton, WA, County=Benewah, State-ID. Source: WWI Civilian Draft Registration. Farmington, WA and just across the state border from Benewah Co., ID. Maybe his farm straddled the state line.
In 1920 Ben and family lived in Garfield, Whitman Co., WA. Ben, b. WA, 30 yrs old, farmer; Effie, wife, b. WA, 27; Delmar, b. WA, 7 and James b. WA 5.
In 1930 Ben and family lived in Diamond Lake, Pend Oreille, WA. Ben, b. WA, 41, marr @ 23, farm laborer; Effie, b WA, 36, marr @ 18; Wallace Delmore, b. WA 17 and James F., b. ID, 14.
You can request an obit from the Washington State Library by sending an EMAIL to AskALibrarian@secstate.wa.gov with Ben's full name, death date and location. They will search the newspaper microfilm for 30 minutes at no charge & reply with what they find.
Regarding Lemuel, I didn't find anything after the 1910 Census. I'd contact the Whitman County Genealogical Society.Successful Hunting!