The Allen (O'Haillin) Family of Donegal

Good day,

I know this is quite a longshot, but I figured it was worth a try. I am trying to locate any information on my ancestors or any potentailly living relatives, distant as they may be. I am descended from the Allen family of County Donegal, which has also been known as Ó hAilín or O'Haillin. 

What I know of my paternal line thus far:

My great grandfather, Robert Allen, was born in Ireland in 1853 and came to America as a baby. His wife was Henriette (maiden name unknown), who is believed to have also been Irish. 

His father was John Allen, born in Derrylough, Co. Donegal, in September of 1819 and he died somewhere in the county in 1880.

And his father, also named John Allen, was born in 1797 and died in 1864. He was burried in Derry, so it is presumable the family lived there for a time or in the northeast Donegal area. His wife was Rebecca Williams, born 1783 and died 1865. 

I know that there was still living family in Ireland well into the 20th century, as my grandfather had correspondence with a relative in the country as late as the 1990s. Unfortunately, my father and uncle burned most of my grandfather's "non valuable" possessions after his death. So, names, addresses, and any other links to family in Ireland were destroyed. 

Any other Irish Allens or O'Haillins out there?