I thought I should come back and post an update about what I actually did. The weather didn't cooperate for a visit to Malahide, so I stayed near cover.

I took a tour of Trinity College and revisited the Books of Kells (having first seen in 25 years ago) - the background exhibition is very nice, especially if you're an illuminated manuscript nerd (like me ). I also enjoyed the Chester Beatty Library, though sadly the roof deck was closed. I also took a walking tour of central Dublin, which took me past many sights I'd seen on past trips, but gave me a bit better sense of history, especially about the importance of the 1916 Rising. Finally, I enjoyed the Glasnevin Cemetery and the botanical garden next door, where I happened upon a free tour and made new Irish friends! The Winding Stair was a great recommendation, and I also tried (and enjoyed) The Sussex.

Thanks again, everyone, for the great recommendations that made my solo trip so much more fun!