Hi Geoco,
To be honest getting back as far as the dates you mentioned is quite a task though not impossible and with a bit of luck and a good bit of research I hope you will succeed.
In your favour are the surnames in Co. Cavan. In 1911 census there are 290 Floods, 236 McEnroe, (though it would have other spelling variants), Galligan beats them at 768, whereas if you had any Reillys you would be looking at nearly 7000.
I would hope that some of them died after civil registration which started for Catholics in 1864 (though some were not registered) from there you can search for free at https://www.irishgenealogy.ie/en/ deaths, marriages and births, the recent ones are not available yet and some images are not online yet, but if you urgently need them they can be purchased.
Do utilise all the records on https://genealogy.nationalarchives.ie, look at the wills and the other records which are all available for free. Prior to cvil registration the church records help fill in some of the missing links. They are available for subscriptions on RootsIreland.ie, you can choose the length of time you wish to subscribe for, again they are not all available, due to lost or indescipherable records, you can check and see what your parish has available. Another source I use is the https://archive.irishnewsarchive.com, it is also a subscription site, very addictive as you get lost in the court cases etc, we were very litigious. The Meath Chronicle and Anglo Celt would be the newspapers for your areas. Also keep an eye out for graveyard transcriptions, they are on various sites, headstones are a great source of information and volunteers go to great lengths to record them, though a lot of that work has stopped in the past year.
You could commission:
Cavan Genealogy
1st Floor, Johnston Central Library, Farnham St., Cavan
Tel: +353 (0) 49 4361094
Email: info@cavangenealogy.ie
You would hope that someone else is connected to some of your family and may have left some information with them, they also have access to books & histories. Do look for stories and journals that are written about your area look at http://www.breifnehistory.com the topics can be quite varied and cover people, events and places.. I could not find Pentalow in 1901 census, though a google search did produce a Patrick in Hartford perhaps you know him. McGinnis has numerous spelling variations, I guess she is your brick wall along with James Smith, perhaps widen your search around them, look for siblings etc and perhaps you can find another way to work them.
I hope I have given you some direction and the best of luck in your research.
Regards Carmel O'Callaghan
