Since I first posted this, I have discovered that James is believed to have been one of the original Sound Island settlers, about 1825 or so. Not sure if he was married before or after he went there: Some relatives think he was, and some think he wasn't, with no proof either way.
There is a story that he was aboard a fishing boat that landed there after being blown off course in a storm. Not sure where they were fishing out of at the time (Burin, maybe?), but the story goes that they liked the island so well that most of the crew came back later, with their families, and settled there. Another version of the story says it wasn't a fishing boat, and they were passengers on their way to Newfoundland (destination port not known) from England. A third version has them on their way back to England, but the "blown off course" and the "return to settle" parts of the story are the same in all versions.
James appears to have been married either shortly before or soon after he settled on Sound Island. Either way suggests that he was familiar enough with Burin to have found a wife there, which implies that he had been in Newfoundland for at least a little while. To me, this would seem to lend credence to the fishing boat theory; however, some of the relatives think that James was a merchant of some sort, rather than an fisherman, which might mean that he was indeed on his way to or from England.
I have also found a bit more about their children. James and Mary Ann had 11 children, all born on Sound Island, for whom I have found records: Amelia, b 1828; Hannah b 1829 - d 1867; Thomas (m Elizabeth), b 1831 - d 1889; Susan, b 1832 - d 1878; Harriet (m. J Rodway) b 1835; James C., b 1838; Joseph Henry (m Charlotte Brinston), b 1840; Mary (m Thos Beck), b 1844; Eliza Ann (m. Henry Beck) b 1845; Francis, b 1847 - d 1872; Sophia (m Wm Eddy), b 1850.
Francis is thought to have died in a shipwreck, but this is not certain. Thomas died in 1889, and his widow, Elizabeth remarried in 1890, to a John Samuel Moulton. Elizabeth's maiden is thought to have been Trowbridge, but this is not certain either.
Giles is a common name in England, with many of them in both Devon and Somerset counties. There are also a lot of them in Kent, but the family stories don't make any mention of Kent, so the "homeland" was probably one of the others.
I love puzzles, but I sure wish the ancestors had left us better clues!