Maria, there are too many John Cavanagh records in Wexford to be definite, and some parishes may not have records, there are 11 between 1839 and 1841 and none appear to be yours, I looked for the civil record which commenced in 1864 but it does not appear to be there, but a genius flash and I tried under Kavanagh, and bingo, do not understand why the name variant did not find it but it is attached, there is good and bad news now, his father is John but her father is not recorded, do not know why.
There are now less John with father John and one possible born in a place called Kilanerin which is north of Gorey but not the places you mention which are south and east of Gorey, I think the place is Banntown and it is a townland bordering Killowen another townland. You will see the location of the various townlands here https://www.townlands.ie/wexford/ You can view the various registers here, only search by date, https://registers.nli.ie/ and you can see the civil records from 1864 here, the church records for Dublin are also here, it is free but sign in. https://www.irishgenealogy.ie/en/ ;
There is a Facebook page on Irish Placenames if you care to join, I am a member but only recently and have not put in a query yet, there are also a number of FB groups doing genealogy by county and in some cases by area but your name of Cavanagh and Doyle are common in Wexford.
There was a land registry carriedout in Ireland and Wexford in 1853, there are no Kavanagh in Banntown, but a number of John Kavanagh in Gorey Barony, leave it to you to search, http://www.askaboutireland.ie/griffith-valuation/index.xml?action=nameS… I so see a John Kavanagh with a landlord Edward Doyle but we are guessing.
Also the civil death records, you can only see the actual cert from 1871 but you could have a go to see if you could pick out his fathers death.
Some rooting around to do now,
Stay Safe
Pat
