This is the information I have:
Thomas Walton Davis is my 2nd great-grandfather. He fought in the Civil War, in the 72nd Regiment of the Virginia Militia (Russell County). He married Isobel Clark. His great-grandfather was Rev. Thomas Davis, who was a Chaplain for the the 1st Light Dragoons (cavalry) in the Revolutionary War. He was also the minister who performed the funerals for both President George Washington and Mrs. Martha Washington. If you're descended from this line, your qualified to join the Sons of the American Revolution, Descendants of Colonial Clergy, and Sons of Confederate Veterans.
Thomas and Isobel's daughter Celia Emerine Davis married Major Otis Caldwell, who commanded the 188th Batallion of the 16th Virgina Cavalry in the Civil War.
Their daughter Margaret Gawanna Caldwell married Henry H. Aston and they had 3 children as you say, except I have Rachel Isabella, not Isabel Rachel.
Henry clearly died between 1900 and 1910, since he appears in the 1900 census, and Maggie is a widow in the 1910 census. Unfortunately, the Virginia legislature decided not to fund keeping vital record information in this time period, so there's not likely to be a death record. There may be a will or probate record, and if so, it would almost certainly be at the Russell County Courthouse.
Some of the Russell County cemeteries have had their headstones surveyed and lists put online. You might try looking at them. It's tedious, but you might get somewhere. Check the Russell County Historical Society website.
For Maggie, it may be a bit simpler. By 1930, Virginia had resumed keeping vital records. The Virginia Vital Records Department in Richmond should have her death certificate, unless she moved out of state or re-married.
Sorry I can't do better.