It's helpful to remember that the Ministers were not native Gaelic speakers and tended to write names phonetically, so there are variations in spelling. The post-1811 Register written by Reverend Findlater was of far lower quality both in terms of record keeping and the paper used to Reverend Thomson's register. The page containing Charles' birth is low quality and contains no more information than is contained in the SP summary - Janet Banton is not mentioned so her maternity must be assumed (given the poor record keeping Robert could have been onto a third wife, but there's no evidence to verify that).
MacHearlish = son of Charles, but you will see it spelled MacCarlish or McShearles. The non-pronounced letters in Gaelic often defeat those who don't speak Gaelic.
For more about the events of Robert Campbell's time in Ireland, you migt want to look at this book -
https://electricscotland.com/history/scotreg/mackay/MackaysHighlanders.pdfIt's lengthy and detailed, and includes the name of everyone who enlisted