I would know much more about the O'Kane family but will try to fill in a bit about the Jones family (Jones will be a lots easier to trace since it isn't that common a name in the area).
Mary Ellen Jones' marriage certificate should list father's name and occupation as well as her residence at time of marriage. The 2 witnesses might also be related to the bride and groom and could be useful clues.
This looks like Mary Ellen in 1911 (latest available Irish census) and 1901-
www.census.nationalarchives.ie/pages/1911/Londonderry/Glenshane/Boviel/904065www.census.nationalarchives.ie/pages/1901/Londonderry/Glenshane/Boviel/1524554From the above 2 records is the basis of a family tree-
___ Jones (d.bef.1901) m. Mary J. (c1862-aft.1911).
1. Maggie Jones (c1886-aft.1911).
2. John Jones (c1887-aft.1901).
3. James Jones (c1889-aft.1901).
4. Bernard Jones (c1892-aft.1911).
5. Mary Ellen Jones c1896).
I can't see a Will/Administration for Mary Ellen's parents but there are 2 men named Jones in Boviel townland in Griffith's Valuation- John Jones and Patrick Jones- who might be connected.
Fortunately PRONI has now put the Valuation Revision Books online which makes it easy to trace the occupier of a property from the printed version of Griffith's until c1930 (within living memory).
http://www.proni.gov.uk/index/search_the_archives/val12b.htmTaking a very quick look at the books, there are several parcels (some just land, etc.) that changed from John Jones Jr. to a Margaret Jones (c1906) then to Mary JOnes (c1909) and then to Bernard Jones (c1919). I didn't try to trace back any further.