I've compiled a listing of battles or the 28th Georgia Volunteers, cross referenced with documentation of Henry and John D. I'll update this post as more information is found. Click it ---> Google Timeline Spreadsheet
Below is the earliest war record of John D Caneega I have. This is muster roll from March 4th 1862, Wrightsville GA, with John listed along with his height of 5- 3.5".
Below is the earliest known record of Henry Caneega's service in the Civil War. This muster roll was found in the Stafford Court House, Stafford Virginia. It notes John was wounded in a battle on July 1, which should indicate the Battle of Malvern Hill.
28th Muster Roll 06/30/1862Found at Stafford, Virginia by Connecticut Calvery.
Closeup of Henry and John D's muster entry.