Hi,
I too have been researching Charles MacLean, the drover, as according to the research by MacLean Bristol, I am descended from him. MacLean Bristol's research paper (Tacksmen of Rum, 2004) identifies John MacLean, Elder of Guirdal (Isle of Rum) as the eldest son of Charles Maclean s/o John 2nd of Grishipol. Unfortunately no other sons or daughters are named in the research paper, but MacLean Bristol includes Hector and Lachlan as two other sons of Charles in a table at the end of the book From Clan to Regiment.
The family are referenced on p402 of Clan Gillean. In an annotation to Clan Gillean, MacLean Sinclair indicates that Charles was married to Janet, youngest dau of Neil of Drimnacross, (correcting/changing his record on p412).
John MacLean (Iain mac Thearlach) married Mary MacLean, dau of Allan (s/o Neil of Drimnacross) - so they were first cousins if Charles' marriage to Janet is correct. John is dead by 1764, and his son Allan is the tacksman of Guirdal at that time according to the 1764 Census of the small isles. Mary is still alive and living with her daughter Florry and Florry's husband Charles at the time of the census.
Interestingly, Rev John (brother to Lachlan and Charles) had a daughter Ann, who married John, s/o Allan s/o Neil of Drimnacross (ie Mary's brother), so it was a pretty tight knit family. Not surprising given that Lachlan, Rev John, Hugh, and Charles were great grandsons of the Laird of Coll (Hector 5th Coll), as were Mary and her brother John great grandchildren to Lachlan 7th Coll.
Hope this is useful (and not too confusing).