We will be in Dublin in September. We already have plans for the major sites that we want to see (National Museum of Archaeology, Kilmainham Goul, Guiness Storehouse, Book of Kells, EPIC, historical walking tour and pubs). However, I believe we have time for one more location and was trying to decide between Dublin Castle or Jeanie Johnson Irish Famine Museum. Looking for recommendations? Thank you!
We were just in Dublin (on a tight schedule) and we loved the National Leprechaun Museum. Definitely unorthodox - along the same style as the "Little Museum of Dublin" with practically no artifacts, etc. but great performance by the guide. We also had time to enjoy Dublin Castle (guided tour) and Museum of Archaeology. Been to all the other places you mention but never been to the Jeannie Johnson display or Guinness Storehouse.
If you don't mind a third suggestion, consider the MoLI Museum, which covers Ireland's substantial contribution to literature: https://moli.ie/. I visited it twice under its old name. I have visited three general literature museums -- in Edinburgh and Chicago, in addition to Dublin -- and around a dozen other literary sites in Europe and the U.S.: The MoLI stacks up very well against them. A related suggestion is to see a play at either the Gate Theater or Abbey Theater in Dublin. The Abbey is the more famous of the two, given that it has mounted plays by John Millington Synge and William Butler Yeats, but the performance of A Christmas Carol I saw at the Gate in November 2002 was probably one of the two best performances I have ever seen.
I really enjoyed my tour of the Jeanie Johnston Famine ship (replica). The guide did a good job of telling the story of this unique ship. Because of the onboard doctor, no passengers ever died, despite awful conditions. Book tickets to secure your spot.