There?s about 42 townlands ending in ?town? or ?ton? in Co Tyrone. The only two beginning with R are Rabstown and Riverstown. Nothing like Renalston.
You can see a list of townland names in Tyrone on the attached link:
http://www.cotyroneireland.com/townlands/townlands.html
The mention of Randalstown Co Antrim is quite interesting because the name Rainey is extremely common in that area.
It might be worth checking the marriage and baptism records for that parish (Drummaul) to see if the family are there. I don?t think any Drummaul records are on-line and so you would probably need to look them up in PRONI, Belfast where copies are held on microfilm. James Rainey to Briget Cullen sounds like a mixed marriage. I can?t see it in the civil indexes from 1845 onwards and that would suggest it was an RC ceremony (or before April 1845 when the records start). Do you know what denomination Jane was? If not, you would probably need to both check RC and the records for the 3 Presbyterian churches in Randalstown plus the Church of Ireland.