I hope you get to make your trip to Ireland and if not this year, perhaps in 2021. Looking at the names you mention I would think that you are very possibly correct in thinking that your ancestors would have Scottish roots and probably be part of the Church of Ireland community in the Parish of Kilglass. The old Church at Kilglass is in ruins and disused since the 1950's I believe. There is a graveyard attached to the church which is still looked after by a few Church of Ireland families in the area. Tashinny Church would be the main Church of Ireland church still being used in the locality.
The records of births, marriages & death for Kilglass are most likely held in the RCB Library in Dublin. If you Google RCB Library, Dublin you should be able to make contact with them but probably not at present due to the lockdown. They would be able to tell you what registers are still existing.
On a brighter note, I understand a graveyard inventory of all the graveyards in the Legan area , including Kilglass, is about to commence which should rsult in a publication in a year tor two.