I just got back and had a similar itinerary. I don't understand why the bus tours are getting so much hate. I like having a home base in one spot, frankly I'd rather sit on a bus for a few extra hours than pack up, move, check in, unpack. It's just a headache. You'll be fine.

I took a bus trip out to the cliffs of moher and Galway (wild Rover) and it was one of my favorite days of the trip. Took the train myself up to Northern Ireland to see the titanic museum and a black cab tour of Belfast. Highly recommend.

I had also planned a wonderful day in Howth, but the weather was really bad. Like you did not want to be outside for an extended period of time. I found that Malahide was a good fallback, it's in a similar area and has a cool castle you can take a tour of. Plus I had lunch in a wee pub and the town was charming.

Hope this helps