Heading to Dublin for work next week. May have a little down time. Any suggestions for things to see/do?

I'm from Dublin so never been a tourist but some things that come to mind would be Kilmainham Gaol (tickets become available everyday), Howth head (outside the city), just walking around the city around Trinity/Grafton street, the epic museum, Guinness Store house, GPO museum tour, loads to do...