Kimberly, thank you for contacting me in regards to the John Fincannon family.Like you, my goal is to also keep my records as historically accurate as possible.
The information you provided matches what I have with the exception that I have John Fincannon's year of birth as abt 1831 instead of 1832.
As for the additional information you requested -
John Fincannon - Enlisted as a Private on 1 Feb 1862 at the age of 30. Enlisted in Company B, 11th Infantry Regiment, North Carolina (Bethel unit) on 31 March 1862. Died 18 Aug 1864 at the Richmond Hospital, Richmond VA from dysentery. Buried in Hollywood Cemetery, Section V, Grave 466, Richmond, VA
Sarah Fincannon - Following John's death, Sarah and her three children moved in with her father (Eliza Hemphill) and their name is listed as Hemphill in the 1870 US Census. The 1880 US Census shows that Sarah and two of her children (Martha Ann and Sarah Elizabeth) are still living with her father, but their last name is now listed as Cannon. The 1900 US Census indicates that Sarah is still living with her father (who is now 88) and her daugher Martha Ann and a granddaughter Cora S., but their last name is listed as Cassaman. The granddaughter's actual name was Clora Selma and she used the last name CANNON when she married Ellis Richard Lingafeldt on 5 March 1905 in Burke County, NC.
Sarah is buried in the Smyrna Baptist Church cemetery in Burke County (also known as the Hemphill cemetery).
William P Fincannon - b. 10 Oct 1861 d. 7 Jan 1879 Also buried in the Smyrna Baptist Church cemetery in Burke County.
(I can send you a photo of those grave markers if you'll provide me with an e-mail address.Plus I can also send you copies of the letters too.)
Martha Fincannon- Martha was never married and her daughter was born out of wedlock.When her daughter (Clora Selma) married my grandfather (Ellis Richard Lingafeldt), Martha lived with them until her death in 1937.She can be found living with them in the 1910, 1920 and 1930 US Census reports. She is buried at the Catawba Valley Baptist Church cemetery in Burke County.
Sarah Elizabeth Fincannon - Married William Pinkney Patton on 11 Aug 1880. She's buried in Forest Hills cemetery, Burke County.
Hopefully this information is what you're looking for.I also have some information on the decendents of Eliza Ann Hemphill and Thomas W Kincaid (who are both buried in the Smyrna cemetery) and I'd be happy to share it with you if you'd like to compare it with what you have.