From my own experience of researching my MacDonald/MacIsaac lines in this area:
Have you come across this site
www.moidart.org.uk Very much my info bible that I used when researching in Moidart. There is a tab on the left for 'Immigration' with info such as this
www.moidart.org.uk/datasets/austemig01.htmGreat photos here of the general Eignaig area - click on individual photos for more info including map of the general area
www.geograph.org.uk/search.php?i=29142444One of the main problems you will have is the fact that your family, like mine, were Roman Catholic. RC records before the start of statutory civil registers (1855) are poor for many areas. Many of these parish registers, not just for the RC Church, have been lost or destroyed over the years. Also, record keeping in registers pre 1855 was variable by church and area. Also, research gets very hard the further back you go generally.
In the last two years or so, the official pay to view site for BMDs, parish registers and original census images
www.scotlandspeople.gov.uk You can register for free and can do some general searches (you have to pay via units to view search results or images). Be aware of spelling variations when searching and use the wildcard symbol '*' when searching names. For example, I would search MacDonald as M*cdon* and MacIsaac, also McKesic/McKissack, as M*c*ss*c. Margaret also often shows as Margret/Maggie etc. so search as Ma*g*.
If you are fortunate to find RC baptisms, this SP help guide is useful
www.scotlandspeople.gov.uk/content/help/index.aspx?r=554&1374 Marriages here
www.scotlandspeople.gov.uk/Content/Help/index.aspx?r=554&2016Have you found the family yet in the 1841 census?
Monica