Firstly, I’d be inclined to order a photocopy of the marriage certificate. You can order a photocopy of the civil certificate from GRO Roscommon for €4 (euros). http://www.welfare.ie/en/Pages/Apply-for-Certificates.aspx
You have to download and print off the form. Then either post or fax it back to them. You can’t e-mail your order to them. However if you want them to e-mail the cert to back to you, they will do that, so tick the relevant box.
That’ll give you a little more information about the Diver/Dever family. For a start it will tell you what the groom and father’s occupations were, which is very important in locating them in official records. Also I think the marriage certificate may contain a townland (ie an address) more than Kilmacrennan. Otherwise you will just be wandering around in a 10 mile area without a more detailed idea of where the family lived.
For example I see 2 Dever families in Gortnaskeagh, who were Church of Ireland. (Most Devers in Donegal were RC). That’s the sort of location you might find on the marriage cert:
http://www.census.nationalarchives.ie/pages/1901/Donegal/Kilmacrenan/Gortnaskeagh/
The Church of Ireland has baptism records for 1818 – 1832 and then 1871 onwards, marriages 1818 – 1830 and 1845 onwards, burials 1818 – 1832 and 1871 onwards. (The missing records were destroyed in the 1922 fire in Dublin during the civil war). From my guide to Church of Ireland records, it looks as though the Rector/Vicar has the surviving records. If you plan to ask to see them there, you should make an appointment well in advance. And expect to pay. The Church of Ireland charges for access to their original records. On the other hand there is a copy of the same records in PRONI (the public record office) in Belfast where you can view them free.
Roger found what seems likely to be Patterson Cheatly’s farm in Dromore. It was plot 9 which was a 42 acre farm running up the hill there. Today it’s not far from Smiths Cottage B & B. You will need to study the Griffiths Map fairly closely and possibly ask locally to find it. It’s about 2 or 3 miles outside Kilmacrenan.
http://www.askaboutireland.ie/griffith-valuation/index.xml?action=nameSearch
What looks to be Patterson Cheatley’s death was registered in Letterkenny in 1872 (Vol 17, page 111). He was 64. There was still a Cheatley family farming there in 1901:
http://www.census.nationalarchives.ie/pages/1901/Donegal/Templedouglas/Dromone/1187550/
William died in 1908. Here’s his probate abstract taken from the PRONI wills site:
Administration of the Estate of William Cheatley late of Dromore County Donegal Farmer who died 23 November 1906 granted at Londonderry to Jane Cheatley the Widow.And in 1911:
http://www.census.nationalarchives.ie/pages/1911/Donegal/Templedouglas/Dromore/497610/
This particular family were Church of Ireland but most of the Cheatleys in Donegal were Presbyterian. So these families are all likely to be descendants of Scots who settled in the area in the 1600s.
If you find the Dever address from the marriage certificate, let me know and I’ll see if I can pinpoint their house.
You ask what to see in the area. It’s a holiday area. Lots of second homes. Most people go for the scenery, beaches and things like the opportunity to hear traditional music in the pubs and so on. The famine museum on the Inishowen peninsula is well worth seeing. (At Christmas it’s magically transformed into Santa’s Grotto which takes a certain amount of twisted imagination but works very well).
I would also drive up to Grianan an Aileach. It’s a Bronze Age fortress on a hilltop and you get magnificent views (when it’s not raining).
https://www.tripadvisor.co.uk/Attraction_Review-g186601-d582480-Reviews-Grianan_Of_Aileach-County_Donegal.html