There was a Richard Workman farming in Crevalea (sometimes Crevolea) in 1832. Possibly related to your family?
In the 1831 census Richard’s family consisted of 3 males and 3 females, plus 1 female servant, all Presbyterian.,
That was the only Workman household in the townland so there seems a high likelihood of it being your family.
Griffiths Valuation of 1859 lists a William Workman in Crevolea. (The only Workman in the townland, suggesting Richard had died and William took the farm over). He had plot 9 which was 16 acres (in 2 separate plots of land). There’s some new housing on the land today. Not sure if the old farmhouse ist still standing. You might need to visit to find out. Modern Crevolea Rd.
William Workman died in 1888 aged 90:
The informant was his daughter Elizabeth English of same townland.
The Valuation revision records (on the PRONI website) show the Workman farm passing to Richard English in 1891. Probate abstract:
The Will of William Workman late of Crivolea County Londonderry Farmer who died 25 June 1888 at same place was proved at Londonderry by Toncus Millar of Crivolea and Stephen M'Alister of Mullan both in said County Farmers the Executors.
The above will is on-line on the PRONI website and in it William leaves the farm to Richard English or Workman, son of his niece Betty English formerly Grissam. It also mentions his nephew William Workman of Mullan.
Workman William George of Mullan county Londonderry farmer died 17 October 1939 Probate Belfast 12 January to Thomas McFall and Edward Heggarty farmers. Effects £413 10s.
14 houses in Crevolea in 1901 with a total population of 76. No Workmans but this English family which contains an Elizabeth English, widow. Born c 1838:
Young Richard English was born in America so presumably the family lived there for a while.
Aghadowey Presbyterian church has no records for the early 1800s. Killaig Presbyterian is nearby and has baptisms from 1805 onwards and marriages from 1836. (Copy in PRONI in Belfast).