Margaret Farrington formally or nee Clarke ?

[Gert in Oz]

Looking at this weeks 3x great grandparent, i have Margaret Clark(e) (1775-1860) married to John Farrington (1779-1860) at Duffield Derbyshire 26 Sept 1818 (IGI submitted). 1851 Census says born Derby.

2 children born William 1817 and Henry 1819 (my ancestor), both born Derby.

Thinking this couple would be in thier 40s when these 2 children were born i went looking for earlier marriages.

From LDS pilot site i found,

John Farrington marrying a Ann Holmes 18 Dec 1802 St Peter Derby, 2 children David 1806-1806 and Edward 1807-1809, the only death i found for Ann Farrington was in 1806 age 16, which i discarded.

!841 census has as you know no relatiionships, but could Mary be Margarets daughter from a previous marriage ?
John Farrington age 60
Margaret Farrington age 66
Mary Clark age 30
Mary Saddall 5

Looking for Mary Clark i found these 2 entrys, note mothers name on the first one, are these the same Mary Clarke and could they be the Mary in 1841 ?.

Name: Mary Clarke
Gender: Female
Baptism/Christening Date:
Baptism/Christening Place:
Birth Date: 13 Aug 1814
Birthplace: BAPTIST,MELBOURNE,DERBY,ENGLAND
Death Date:
Name Note:
Race:
Father's Name: Job Clarke
Father's Birthplace:
Father's Age:
Mother's Name: Margrate Wakefield
Mother's Birthplace:
Mother's Age:
Indexing Project (Batch) Number: C09111-1
System Origin: England-ODM
Source Film Number: 590684
Reference Number:
Collection: England Births and Christenings, 1538-1975

Name: Mary Clarke
Event Type: Birth
Birth Date: 13 Aug 1814
Birthplace: Melbourne and Ticknall, Derbyshire
Christening Date:
Christening Place:
Marriage Date:
Marriage Place:
Death Date:
Death Place:
Burial Date:
Burial Place:
Father's Name: Job Clarke
Mother's Name: Margaret Clarke

Please tell me i`m on the right track before i go insane.