At least some of the children were baptised in Harbottle Presbyterian church:
Lancelot 3 Aug 1830 s. of William & Isabella Laidler, Raw, Par. of Elsdon, father a Shepherd
Elizabeth 28 Nov 1831 ditto
Sarah 8 Mar 1838 d. of William Laidler & Elizabeth Brown (sic) Ilelaw, father a Shepherd
Isabella 8 Jun 1840 d. of William Laidler & Isabella Brown, Grasslees, father a Shepherd
17 Apr 1843 William ditto father a Husbandman
Isabella and Elizabeth are sometimes used interchangeably but I would not have thought a family using both names for different daughters would have done this for the mother. Mistake? Or preference of Minister?
Marriage may have taken place over the Border. Worth checking Scotlandspeople just in case but probably not C of S. Have seen references to Presbyterian Ministers taking couples over the Border to marry them, and also of course it may have just been a marriage before witnesses.