Madden Family from Kings (Offaly)

I am trying to trace my Madden family.  My great-great grandfather was John Madden.  He was born about 1824 in what was then Kings County.  He had an older brother, James (Shamus) born between 1822 and 1824), sister Elizabeth born 1834, sister Catherine.  Possible two other brothers or cousins named Patrick born about 1832 and Michael born about 1837.  We believe they came from around Banagher but not sure.  An article about Elizabeth's husband who was a prominent builder in Toledo, Ohio USA said that Elizabeth was born Kings County, Ireland, date of birth was May 10, 1834 and listed the village or town as a name I could not find on any map or information about Kings County.  However, the spelling made me think that the person writing the article did not know the spelling for Banagher and tried to do the best he could on the name.  From what I remember hearing from my grandmother and her brothers, their grandparents did not talk about the home country and as far as I know no letters or keepsakes were handed down to their children.  John came over before 1850 has he appears on the 1850 U.S. (Ohio) census as does James and Catherine.  I am not sure about the dates of arrival for Patrick, Elizabeth or Michael.  I have a hand drawn family tree that came from a distant cousin under Elizabeth and it shows James, John, and Catherine on it as sibblings.  I only have a portion of it so not sure if Michael and Patrick are somewhere on the section I do not have.  My grandmother said that the story that was passed down to her was that they came over due to an argument about a stolen cow and there was a death involved.  Not sure how much of this is credible but thought it might help in locating any information about John or his family.  I am hoping to come to Offlay perhaps next spring if the virus allows safe travel between the U.S. and Ireland.  If I can find out more about my Madden family, I would love to be able to share with other Madden cousins who have also would like to come to Ireland to see where their roots are.  Any information anyone can give me would be greatly appreciated.  Also, who should I contact to see about my visit there.  Would I fly into Dublin and then a short flight to Offlay; or a train trip or a bus?  I know the county has a visitor's center but having information on the best and easiest way to get to where I want to go would be a blessing.  Thank you for any help you can give me.  Shirley Baker