Malcolm John McKendrick (1775 - 1859) is my GGG Grandfather, Margaret was his daughter by his first marriage (Nancy McKay), and I'm descended from Malcolm through his second marriage (Cathering MacLean). Thus Margaret is my GG Half Aunt.
Like you, I don't know Margaret's dob, but as you say, her husband Hugh MacLean was born about 1783. His birthdate makes me thing they were likely married about 1805 or thereabouts, so I'm not sure about their first child being born in 1822. I have a note that Donald was born in about 1802 and Hugh in 1831. Eleven children in 28 years sounds about right (for that day and age anyway). I have no information at all on that family except the names of their 11 children.