I don't think Lucinda survived the early years of her marriage.
1880 Roscoe, St. Clair, MO Tandy, Wm 42 MO VA VA Mary A. MO MO MO John J. 3 MOMO MO Martin L. MO MO MO
(St. Clair Co. was where William's brother John F.lived.)
1885 Opolis, Crawford, KS Tonday/Tanday, W. H. 49 KY (to KS from MO)Insurance Agt. M. A. 27 IA J. G. 8 (male) KS M. L. 6 ( Male) MO R E. 4 (Male) MO O. E. 2 (female) KS L 1mo. (female) KS
William was admitted to the Home for Disabled Volunteer Soldiers in Leavenworth KS in Feb. 1889 & died there Sept. 6, 1892.Their records indicate he was a widower.His next of kin is shown as brother John F. in Osceola, St Clair Co. MO.
I don't find the kids in 1895 KS census.In 1900 there is an Olive E. Tandy b. Feb. 1884 KS at the Soldiers & Orphans home in Atchison Co. KS.She is only 16 but shown as an employee/attendant.
There is a John G. (Gyles) Tandy b. 2/14/1878 (Indian Terr.) who appears in Story County Iowa @ 1910-1925 time frame.He married Isabelle Manion and had several children before her death in 1924.In 1925, some of their kids appear in foster care.
In 1925 IA Census John G. says his parents were Wm H. Tandy and Lina/Lena Cole.
Lina is often short for Wilhelmina, Magdalina, Angelina, or Avalina.This may be the Mary A. that William was married to.
It appears that John remarried -probably in Polk County, Iowa and died in Polk County Iowa 2/8/1943.He is buried at Glendale Cemetery in Des Moines, Iowa.
I suggest trying to get a death certificate for John G. Tandy and/or contacting the cemetery, as they may have more information.