Maybe your Newgrange tour could include The Hills of Tara and the Boyne Museum. The Dead Museum, and Dublin Castle are also interesting. Don't forget EPIC.
On our last trip we found ourselves outside The Leprechaun Museum and went in to kill some time before meeting friends. It was quirky and and a little spendy @ 16euros. A guide escorts you through three rooms (more like play scenes) and tells an appropriate folktale in very dramatic fashion. There are no exhibits except each room mimics something, like the interior of a blackhouse. My wife and I rarely agree on how much we enjoyed the visit. We would go back to do a repeat with a different guide, since the stories change.
The Little Museum of Dublin has a similar approach, with a highly talented guide walking your around a few rooms heavily decorated with knick-knacks. Also memorable.
My wife went to Dublinia while I sat nearby in the Brazen Head claiming a table for the music, and she thought it was fabulous.