Hi Anne
Have a look at the following website:
http://freepages.genealogy.rootsweb.com/~ked1/41ftwillcen9.htmlThis site cover the census for 1841 for the Fort William area of Inverness-shire and includes most of Moidart/Ardamurchan. The URL above is for page 9 which covers this area.
I have a hunch that your Mary's family are probably from the Aris Kinloid area included above. See below for an entry for Hugh MacEachan which could be her father (no mention of Catherine so she could have died by then). The 1841 census index doesn't give as much info as the 1861/81 but something is better than nothing!
ARIS KINLOID 11 HUGH MACEACHAN M 70 FARMER Y
ARIS KINLOID 11 ANNE MACEACHAN F 50 Y
ARIS KINLOID 11 DONALD MACEACHAN M 35 Y
ARIS KINLOID 11 ARCHIBALD MACEACHAN M 30 SHOEMAKER Y
ARIS KINLOID 11 ANNE MACEACHAN F 25 Y
ARIS KINLOID 11 ALLAN MACEACHAN M 10 Y
ARIS KINLOID 11 JANET MACEACHAN F 8 Y
MacEachan and Smith are not that common in the area so you can find them easily enough and hopefully make some connections with the name of children etc.
In respect of education, you would be surprised by how much they were trying to do at the time. Have a look at the following site:
http://www.moidart.org.uk/. Click on the Education button in the front menu for an overview of schools and educational activity in the area during the early part of the 19th Century. This site also has information about Catholic churches in the area.
Good luck!
Monica