Hello Joan

1881 UK census ( April 3rd)Thomas Ardern and wife Christian , aged 37 and 36 are at Sterne Terrace, West Derby, with children Robert K, 14, Kate Ann, 10, Caroline Ada 9, Florence 4, Alice 2 and Daisy Dora 1, along with Thomas' B-I-L Alfred Carphoy (Curphey ?) aged 26 , all born Liverpool, except Christian born Douglas IOM.
Found a christening of a Thomas to them in Fairfield 11/4/1871 , but could not find a death for him as he is missing in 1881.
Could not find any of them on 1891 UK Census.
The 1881 Canadian Census was started April 4, but there seems to be closure date.
I can find no trace of any of the above family in Canada 1891 or 1901, no deaths or marriages (1885-1925) of the girls, same applies to the USA Census of 1890 and 1900 and marriages.
Looked on 1891 & 1901 CC for any female Christian born IOM or England and found none anything like Ardern.
On the 1891 C.C 64 people of any name identify as born IOM , and in 1901 54 people, but nothing like Christian Ardern.
Also looked for Arden, Adern and a few other variants.
Looked in Australia and New Zealand at lot more Ardern's , particularly in NZ , but no matches.
The current Prime Minister of NZ is Jacinda Ardern.

It is going to be difficult to find them.

Cheers
David Dwyer