I discovered that Ardersier in Moray was formerly called Campbelltown.
Yes and no.
It is true that Campbelltown is now called Ardersier, but it is not true that Ardersier was formerly called Campbelltown!
The explanation of that slightly bizarre statement is that the
village now known as Ardersier was originally called Campbelltown, but the name Ardersier applies to the whole
parish, and it long pre-dates the development of the village of Campbelltown.
Writing in 1792, the Rev Pryse Campbell says, "The number of inhabitants, according to the oldest people now alive, would not exceed 300, 60 or even 50 years ago. Dr Webster's state" [1755] "was 428; the amount of the inhabitants now is 802. Males 385; females 417. In the village of Campbelltown, which owes its birth to the garrison of Fort-george, there are 293 souls. The garrison of Fort-george, exclusive of the marching regiment stationed in it, but including 3 companies of invalids, consists of 496 souls, of whom are 246 males, and 250 females". See stataccscot.edina.ac.uk/static/statacc/dist/viewer/osa-vol4-Parish_record_for_Ardersier_in_the_county_of_Inverness_in_volume_4_of_account_1/
Fort George was built after the Jacobite Rising of 1745 as part of the government's policy of suppressing Jacobitism and the clan system.
Also the parish of Ardersier is in the county of Inverness, not the county of Moray. In religious terms it is in the presbytery of Nairn and synod of Moray.
Scotland's People's excellent records aren't infallible - two of his definite grandchildren don't appear in them either, but do in IGI - another complicated story!
I hope that you have tracked down and checked where the information in the IGI about those grandchildren came from. The IGI, as its name suggests, is an
index, not a primary source, and while a lot of the information on it relating to Scotland is correct, there are some very dubious bits of information on it. (If you don't believe this, do a search for given name Odin, birth in Norway, 0100 to 0700, and see what you get.)
In general, do not trust anything you find online unless it is an image of an original document.