Hello
Not sure if you are aware, but there are at least 21 "family trees" appearing on the ancestry.com website, for the Family of Robert Linton BLATCHFORD and wife Flora Lilian/Lillian (nee JUDD).
Quite a number of these trees have rather huge numbers of people attached to them, so they may be "collections of random names" rather than "family histories", as such.

I only looked fleetingly at some of them, and couldn't see anything relating to the children of above-named BLATCHFORD's. And of course the grandchildren's names would not be shown in these trees, because they are likely to be living. Still it may be worth looking over these "trees" - someone may just have the information you are wanting.
With your search being for probable "living persons", we here are not really able to help very much, and certainly the names of "the living", are not permitted to be published in threads in this RootsChat forum. Further, many records > electoral rolls, online newspapers, etc. > are not yet available for searching online, in the time frame you would be needing.
I'll add a few other suggestions for searching in following post.
~ Lu