To go backwards I can only suggest trawling the PRONI and National Archives for your family name and townland locations. Remember to use all know variant spellings as searches for McGurren will ignore McGurn, Magurn and so on. You can search leaving names blank and putting just the family name or location in the Full Abstract field. This will bring up wills of anyone who mentions the family or location specified.
http://applications.proni.gov.uk/DCAL_PRONI_WillsCalendar/WillsSearch.a…
http://applications.proni.gov.uk/DCAL_PRONI_WillsCalendar/WillsSearchIm…
Is an image of a will of Bernand Keenan of Rossavilla.
You can also trawl the ecatalogue using family names or townland names.
http://www.proni.gov.uk/index/search_the_archives/ecatalogue.htm
National Archives have put the will calendars online but not the actual wills themselves.
http://www.genealogy.nationalarchives.ie/
As for going forwards from 1911 your best bet is to find an elderly local who may recall the McGurns/Keenans.
I am not sure if there is any specific who is monitoring Cleenish Parish or whether it will end up coming back to me.
Bob