In case someone else is looking at this in the future, I'll set out what I have (which by the way is all set out on the FamilySearch tree which I referenced earlier in this thread):
1772 Kilmory Kirk Session Minutes:
January 23rd, DANIEL McNEIL in Kildonnen and his spouse ISBEL CRAUFORD rebuked for antenuptial fornification
1773 Bap of dau Mary, to Daniel McNeal & Isabel CRAWFORD, in Kilmory
1775 Bap of dau Cathrine, to Donald McNeil & Isabel McGRAFFAN, in Kilmory
1778 Bap of dau Mary, to Donald McNeil & NcGRAFFAN, in Kilmory
1780 Bap of son William, to "Donald MacNeil & Isabel CRAWFORD his wife in Dippin" [per actual Record], in Kilmory
1784 Bap of son Allan, to Donald MacNeil & Isabel CRAWFORD, in Kilmory
1787 Bap of son Robert, to Donald MacNeil & Isabel CRAWFORD, in Kilmory
1790 Bap of dau Janet, to Donald MacNeil & Isabel CRAWFORD, in Kilmory
1792 Bap of dau Janet, to Donald MacNeil & Isabel CRAWFORD, in Kilmory
1796 Bap of son Donald, to Donald MacNeil & Isabel CRAWFORD, in Kilmory
(So there were actually two children recorded with mother as McGraffan - so not just a one-off error)
1841 Census at Dipping, Kilmory, Bute:
ROBT McNiel, 50, Farmer, born Bute [son Robert b1787]
CATHARINE McNiel, 65, born Bute [dau Catherine b1775]
Janet McNiel, 10, born Bute [dau of son Allan b1784]
1851 Census at Dipping, Kilmory, Bute:
ROBERT McNiel, head, 63 [c1788], single, Pauper Formerly Farmer, born Dipping, Bute [son Robert b1787]
CATHERINE McNiel, sister, 75 [c1776], single, Pauper, born Kildonnan, Bute [dau Catherine b1775]
[Their birth places tying in with the parents initially being in Kildonnan (per 1772 Kirk Session rebuke) and then being in Dipping (per son William's 1780 bap)]
1858 SP Death Index: ROBERT McNeil, age 70 [c1788], mother's maiden name Crawford, in Kilmory, Bute
1858 SP Death Index: CATHERINE McNiel, age 82 [c1776], mother's maiden name Crawford, in Kilmory, Bute
Cheers
John