I visited Dublin in October 1997 and November 2002. I found Dublin just as fun in the latter part of the year as it was during my three summer visits.
In fact, my fondest memory of the Irish capital was during the November 2002 visit, when I saw a performance of A Christmas Carol at the Gate Theater in Dublin. It was the best of at least 300 plays I have seen in my life. Whether the Dickens play is showing or not, it's worth seeing a play at the Gate or Abbey theater.
I went to a Evensong performance at Christ Church Cathedral as part of my 2002 visit. It was among the most moving religious experiences of my life.
All the other Dublin stuff I would recommend is in tourist guides.
Since you like antiquities and nature, it's worth visiting Glendalough (https://glendalough.ie/). That holds dozens of antiquities, some, I believe, around a millennium old. Glendalough is a monastic site about 30 or so miles south of Dublin in the Wicklow mountains. St. Kevin founded the site in the Ninth century or thereabouts.
Glendalough is surrounded by dozens of trails, including the Wicklow Way (https://www.wicklowway.com/). I walked the entirety of the 100-mile-long Wicklow Way in 1999. The trails around Glendalough are especially nice.
Since you like nature and antiquities, it's also worth visiting the Boyne Valley area north of Dublin. You could see the Hill of Knowth and Newgrange -- amazing burial grounds older than the pyramids in Egypt -- and the Hill of Tara, the ancient site of Irish kings, as well as other sites. You could probably arrange a day tour of the Boyne area with a group via the Dublin tourist information office downtown. You could also arrange a tour of Glendalough at the same office.
Since you might rent a car, it's work visiting the Rock of Cashel (https://heritageireland.ie/places-to-visit/rock-of-cashel/). It's about 2 or so hours away from Dublin.
Be very careful driving in Ireland! People drive on the other side of the road (if you're American). I rented a car twice in Ireland, but it takes getting used to.
