We’ll be taking the RS Ireland 7 day tour in early Sept, and staying 4 extra days in Dublin after (6 adults). Will see Kilmainham Gaol, Trinity College/Book of Kells with the tour, and am trying to come up with an itinerary for our 4 extra days. Would like a day trip (or overnight?) to Belfast. Any suggestions would be greatly appreciated!
It would help to know what your interests are. There are lots of things to see and do in and around Dublin and Belfast. Whether you should stay over in Belfast really depends on whether you can see everything you want to see in a day trip. The idea of not changing hotels again would appeal to me after moving so quickly through the country. Have you already booked an extension of your stay at the tour hotel or will you be moving anyway? In that case, maybe moving up the Belfast makes more sense. Would you consider getting a van and making it into a road trip up to the Giant's Causeway?
My trip report from this past May might give you some ideas:
https://community.ricksteves.com/travel-forum/trip-reports/solo-in-ireland-may-2025-my-trip-report
We stayed in Belfast three nights. One day we enjoyed a Black Cab tour and the Titanic Museum. The other full day we took a day trip to Giants Causeway (and a couple other stops) and also liked that. Probably depends on your interests. We took a bus to and from Dublin and it was hassle free and easy.
Which company did you use for the taxi tour in Belfast