In respect of Isabel Gourlay and Alexander and children, again from IGI, all actual extracts from the OPRs:
ALEXANDER AITKEN Marriages: Spouse: ISABEL GOURLAY
Marriage: 27 FEB 1789 Carnbee, Fife, Scotland
Children:
1. WILLIAM AITKEN Birth: 21 APR 1798 Christening: 16 MAY 1798 Carnbee, Fife, Scotland
2. ROBERT AITKEN Birth: 13 FEB 1796 Christening: 21 FEB 1796 Carnbee, Fife, Scotland
3. DAVID AITKEN Birth: 28 MAY 1800 Christening: 14 JUN 1800 Carnbee, Fife, Scotland
4. ELIZABETH AITKEN Birth: 10 MAR 1792 Christening: 25 MAR 1792 Carnbee, Fife, Scotland
5. JANET AITKEN Birth: 27 APR 1790 Christening: 02 MAY 1790 Carnbee, Fife, Scotland
6. ALEXANDER AITKEN Birth: 10 MAY 1794 Christening: 25 MAY 1794 Carnbee, Fife, Scotland
From the 1841 Census, this looks like Isabel and some of the Watson grandchildren:
AITKEN Alexr. M 35 Farmer Fife
WATSON Alexr. M 9 Fife
WATSON Aitken M 5 Fife
GOURLY Bell F 60 Fife
AITKEN Elisabeth F 37 Fife
WATSON Jane F 15 Female Servant Fife
WATSON Georgina F 11 Fife
Address: Carhurly, Kingsbarns-Fife
There is a death entry showing on Scotlands People, the official BMD and census site which is pay to view. I haven't viewed it just done the searches. The entry is in Carnbee for an Isabella Aitken other name Gourlay in 1855, with a birth year of 1770.
You are so fortunate to have found Isabella's grave. You might also want to view the actual cert. In 1855, the first year of official registration in Scotland, the BMDs are a wealth of info. By 1856, the info contained in these certs. had been pruned down from two pages to one. Certainly worth a look!
In respect of the 1851 Census, I don't have access to it. I can see, however, an entry for an 80 year old Isabella Aitken in Carnbee from the free searches on SP.
Regards.
Monica