I will have to check this to make sure, but I think the Cherokee VANN family had left Georgia by the late 1830's. They are extremely well documented.
By 1880 there are no HELTONs in Murray Co, but there are 245 in various other parts of GA. 241 of them are white. 4 are black. In fact, Jahial HELTON, and his descendants are never anything but white !
Within the VANN family, Joseph and James are, as I'm sure you know, very popular names. Chief James VANN 1766-1809 (Killed at Buffington's Tavern) and his son Joseph "Rich Joe" VANN 1800-1844 (Died when the steamboat Lucy Walker exploded near albany IN) were both extremely well known in the area.
As Jahial HELTON came to GA from SC sometime in the 1830's, I think a connection to the VANN family would be unlikely. And I don't think any of the Cherokee VANNs were "Full blood". Again, it's something I must check out.
For an excellent source of accurate information check out Jerry Clark's messages on this forum. A very dedicated and diligent researcher.