If you like to see museums I recommend you Dublinia because you can learn history about viking, middle ages and archeology while you play and do interesting things.
The city centre of dublin is small but there are alot of things to do.
And other option is to visit the Trinity College that if you didn´t know it, it is an university. Where you can visit the book of Kells and a very big library where the film "Harry Potter" was film.
ALICIA