I believe the EPIC - The Irish Emigration Museum is open on the Bank Holiday, well worth a visit. You can book tickets in advance.
The EPIC Museum is located on Custom House Quay, and also close to the Jeanie Johnston Emigration ship, also worth visiting if it's open - It's usually open 7 days so should be operating on the Bank Holiday.
I've read that the most visited location in Dublin is the Guinness Storehouse , home to Dublin 's best known business - it's a tour that shows the history of the brewery going back to 1759, I checked and there are still some slots open for the 31st.
The city may be a little quieter than usual on a Bank Holiday, larger shops may be closed, but there should be restaurants open, and while some transport options start a little later in the morning are less frequent there will still be Luas (trams) and Dublin buses operating. The closest Luas stop to the EPIC is at Busáras (Bus Station).
It's only about 3km (less than 2 miles) from the EPIC to Guinness Storehouse, if you opt to walk I can list a few historic buildings etc you can pass on the way... let me know...