Cath's bapt on 24 Oct 1819 Kirk Rushen has her father as William KELLY and mother Sarah WATERSON. John bapt 13 July 1823 Kirk Rushen (Sarah's surname not given).

The children's ages given in 1841 are pretty accurate. As well as Cath and John, the IGI extracted records have Ann bapt 1819 (no mother's surname given), Sarah 1825, Margret 1829, Elizabeth 1831, and Henry 1834.
There were two older children, William 1816 and Jane 1817.

William Kelly & Sarah Waterson married on 9 Dec. 1815 Kirk Rushen.

You said you had an 1854 marriage for your John Kelly? What was his father's name and occupation given there?
(On IGI the marriage date is 27 May 1855 Malew.)

Sue