Hi Matthew, I have been a member of Ancestry on and off for a few years but my membership ended in December.
Below were the only records I could find on SP for CHARLES CLARK/ISABEL MACHRAY, all born Aberdeen. There was also two in 1826, &1829, for a CHARLES CLARK/ISABEL ANN CLARK and another in 1826 for a CHARLES CLARK/ISABEL CORMACK
ALEXANDER 1825, ISAAC1826, HELEN 1829, PETER 1832, MARGARET 1834. – You noted they had 3 boys & 3 girls, one girl missing, that could be MARY 1827 but mother noted as Isabella Clark?
I also saw the 1851 census on freereg that Monica posted and it certainly looked like the Isabella birth in Aboyne I posted, as did the two eldest children listed Helen & Peter. but I could not find suitable records for the other 4 children lised.
Perhaps you might know of them?
Colin