Thanks to Cousin Muriel, there is something new to add to the blog:
The Civil Registration for Michael McMahon's and Mary Mullaney's (also known as Blunney later in her life) wedding on 7 February, 1882.
I'm wondering if the Patt O'Neill is related to the young lady who came over with Mary and the younger children.

There is one problem. It seems that the Baptismal record I found for Michael (and posted in this blog) was not for the correct Michael McMahon! Michael's father is listed as John McMahon (deceased). We have more work to do!