Mac Dougalls from Omagh

I am trying to research the family of my grandmother who were Mac Dougall (mc Dougal) living in Omagh.

Her parents were Robert Mac Dougall and Margaret Mc Corkell

Brothers and sisters were:

Eliza born 3.4.1868, John - 19.4.1870, Robert 8.5.1872, Catherine Mary (my grandmother) - 9(19)12.1874, John - 1877, Ethel 3.7.1885 (and Married a George Lee), William 8.6.?, Margaret 8.12.? (married Edward Goligher), Laura 1890 and Donald 1891. 

Margaret Mac Dougall nee Mc Corkell died on the 5 December 1905 and the son Donald was present at the death of his father on the 20th May 1908, the address given at the time of their deaths was John Street, Omagh.   MBy the time the 1911 census was taken the only children I could find were Ethel Mac Dougall and Margaret who had married Edward Goligher and they were all living in Derry.

I am particularly interested in trying to find out what happened to the two younger children, Laura and Donald who both seem to have disappeared completely.   I'given up on the rest of the family, think they all retreated back to Mars!!!!

I am also interested in trying to find more information on both the Lee and Goligher families.

Any advise would be greatly appreciated.

Norah