Hello Dean,
I have good news for you. I know where Mill Farm and the nearby derelict Mill is situated near Killead, in Antrim. I'm 99% sure this is the Farm and house you've been searching for, and it's still there! You may be able to view photographs of the house on Streetview or Goolgle Earth! 😁
The address is -
MILL FARM
39, Antrim Road,
Aldergrove,
Crumlin
ANTRIM
BT29 4DY
Northern Ireland
United Kingdom
Google earth with this address detail, let's you view the side gate entrance to MILL FARM. (The Farm name is on the gates.) Move the cursor towards the Antrim Road, then turn left. On this road move the cursor on slightly 2 or 3 times,then swing round to view the house on the left with a central arched window. This house, barns and outbuildings are what you've been searching for, MILL FARM.
It's about 5 miles as the crow flies to Killead, which is a small hamlet, Killead Presbyterian Church with which your family had connections, is in the centre of Killead. You wouldn't be able nowadays to travel by road from the house to the church in a 'straight line', as there is an airport, BELFAST INTERNATION AIRPORT situated between the two,hence there would be a slight detour around the Airport.
I live in the area, that's how I noticed the name, 'Mill Farm' on the gates!
HOPE this helps you in someway.
More info for you at the Church:-
Grave of William McElrath, MILL FARM.
Containing an inscription to:
Robert Harper McElrath Royal Dublin Fusiliers killed in action 21st October, 1918 aged 32 years, youngest son of the late James McElrath buried in Dadizeele Cemetery, France.
"His duty nobly done."
The following details are from the Commonwealth War Graves Commission and is reproduced with their permission:
Robert Harper McElrath, Private 25459.
1st Bn Royal Dublin Fusiliers.
Grave/Memorial reference I.B.30 Dadizeele New British cemetery.
Son of the late James and Mary McElrath, of "Mill Farm", County Antrim.
Regards