Hello,
I can only find one Milne burial in Bo'ness, none in Carriden:-
mural winged soul, skull, barley sugar pilasters, Andrew Milne late merchant Bo'ness, 27th Oct 1817 aged 70, wife Mary Learnmonths died 27th Nov 1832 aged 72, also here interred son James 4/1/1825 aged 24 and other four of their children died in infancy.
The IGI has a William Milne son of Alexander and Susan Swan death date either 27th Feb 1825 or 27th Jan 1826. neither of these options came from parish records.
I can't find any deaths in either Stirlingshire or West Lothian for either Alexander of Sarah.
sorry I can't find anything on them. Regards ... Meg