What sights in Dublin would you recommend for a 12-year old? My wife, daughter, and I have about five days in town.
The Archaeology Museum is very worthwhile, and I think it's quite accessible for a twelve year old. Lots of bronze age artifacts, jewelry and Celtic ornamentation. Also there is Gallagh Man, a bog body that is remarkably well preserved. Nearby is the also interesting Natural History Museum, and Saint Stephens Green.
Depending on your daughter's interests, the Kilmainham Gaol tour may be a good idea, it's a pretty good start to understanding the Troubles.
Might suggest that your daughter look at this list of attractions for Dublin and decide what may be interest to her:
https://www.tripadvisor.com/Attractions-g186605-Activities-Dublin_County_Dublin.html
We were just there 2 weeks ago and my kids aged 8 and 11 really enjoyed Dublinia. My 11 year old loved Kilmainham gaol... it made for a very interesting conversation about history and the treatment of different groups etc. It was a little much for my 8 year old.