Lori,
I may possibly have found your family in the townland of Greenshields on the outskirts of Ballymoney.
In 1817 a new Minister took over at Ballymoney 1st Presbyterian church. Rev Parkes decided to conduct a full census of everyone in the parish (of any denomination). No privacy or data protection laws then but we are indebted to him for asking people for their private information.
In Greenshields in 1817 there is a family consisting of Andrew Campbell (head), Charles (son), Margaret (daughter in law) and 3 grandchildren Andrew, John & Mary. This appears to match your information pretty well perfectly. There were several other Campbell families in the parish but no other Charles, never mind one with a wife named Margaret. I feel it’s probably your family. Parkes census, as it’s called, is on Bill McAfee’s website:
http://billmacafee.com/19centurydatabases.htm
There was also a Lamont family in Greenshields at the same time, headed by Richard Lamont. However he had an unmarried daughter called Margaret in 1817 so it can’t really be your Lamont family, as your Margaret was evidently married and had several children by that year. The surname is fairly common in the area though and Margaret’s family likely lived nearby. At that period when most courting was done on foot, you often married the girl next door.
In the tithe applotment records for 1825 Charles Campbell is listed as farming Greenshields. No mention of Andrew, suggesting he had died and Charles had taken the farm over.
http://www.irishgenealogyhub.com/antrim/tithe-applotments/ballymoney-parish.php
No Campbells in Greenshields in Griffiths Valuation of 1861 indicating they had either died out or moved away.
You haven’t said what denomination the Campbell & Lamont families were, though I’d hazard a guess they were Presbyterian. In which case you might want to search church records for baptisms for the other children, as that ought to confirm you have the right family. If Martha was born c 1822 and baptised in that church, the record may exist.
Ballymoney 1st Presbyterian church has records of Baptisms, 1751-71, with gaps, and 1817-1926; & marriages, 1817-1926. (Presbyterians generally don’t keep burial records). There’s a copy of the records from 1817 onward in PRONI (the public record office) in Belfast. The Minister has the baptism records for 1751 -71 (which are fire damaged).
Ballymoney was heavily involved in the 1798 United Irishmen’s uprising and the town was burned as a reprisal. Most of the Ballymoney Presbyterian church records were lost in the fire, though a few years baptisms were saved.
If you are unable to go to PRONI yourself, you could employ a researcher. Researchers in the PRONI area: http://sgni.net
Turning now to the question of whether Margaret Lamont was born in Scotland, the general background here is that most of the population of Ballymoney and the surrounding area are descendants of Scots who arrived in Ireland in the 1600s or sometimes, especially around north east Antrim, in the late 1500s. In North America these are generally referred to as Scotch-Irish. Here in Ireland we tend to call them Ulster-Scots. Researchers in other countries are often aware their Irish born ancestors may have come from Scotland and start searching for births in Scotland etc. It’s perfectly possible that Margaret Lamont was born in Scotland in the late 1700s but I think it unlikely. I think she was probably born in Ireland to a family whose ancestors arrived in the 1600s. By the 1700s and early 1800s, the Scots settlers were dissatisfied with life in Ireland and were leaving again. That’s not to say the odd Scot didn’t arrive then but it would be very much against the prevailing flow.
The Campbells may also have arrived at that time or perhaps even earlier. The Campbells ancestral home is Inveraray in Argyll. (The clan chief the Duke of Argyll still lives there to this day). From the Mull of Kintyre in Scotland to Torr Head in Antrim is about 9 miles. These are not big distances. The Campbells came to Ireland for various different reasons. Some in the 1300s and 1400s as galloglass (mercenaries) but later arrivals were often from Kintyre (and were often Presbyterian) and were part of the settlement of the area.
There are no records for the Scots settlers who arrived in the 1600s, nor any baptism or marriage records for their early years in Ireland. In fact few churches in Ireland have many records before 1800, if that. What folk sometimes start doing is search the internet for likely events for the names they are looking for, and find records of people with those names in Scotland from parishes that do have some records for that period. With common names like Campbell & Lamont/Lamond, this can lead to errors. (There were a couple of hundred Margaret Lamonts in the 1841 Scottish census. There would have been just as many in 1790. Easy to latch on to the wrong one). You mention that you have not been able to find any documentation showing place of birth. To me that suggests someone somewhere has perhaps been guessing or accepting Ancestry’s hints.