The only Samuel Caddy recorded as married in Cornwall around that time was
one Samuel Caddey, married in the Penzance district in the September
quarter 1861; I do not know his wife's name.
The 1881 census transcription contains an entry at RG11/2343 f 109 for what
may well be the family of Louisa, widow of John, though the younger
children do not quite match. In particular, William aged 3 is shown as her
grandson, rather than her son.
It shows also a Samuel Caddy aged 48, born St. Hilary, but his wife is Ann
(RG11/2343 f 110). I cannot find the death of a Louisa Caddy between 1861
and the 1881 census, nor can I find a likely Louisa Caddy in the
transcription.
If information on births, marriages, deaths of Caddys from the middle of
1837 or probates or administrations after the 9th January 1858 is of use,
let me know. I do not have any purely Cornish sources, though. If you can
trace any descendants in the male line to beyond 1911 I may be of greater
help.