For Dublin, I would try TripAdvisor and look for day tours. I would recommend a private or small group tour as they seem more flexible in picking up at your location. The big bus tours have pre-determined pick-up locations in Dublin which would be a pain as you would have to take a bus or the DART into Dublin to meet the bus. If you are docking in Dun Laoghaire, I would suggest a tour to Powerscourt Gardens, Glendalough, and the Wicklow Mountains. Newgrange, Knowth, and the Hill of Tara are also an option. I would second ToursByLocals. I have used them in other countries and have been very pleased. I would recommend www.TourDublin.ie for tours out of Dublin. I have used this company several times in the past and have recommended them to friends and family. Whatever you decide I'm sure you will enjoy Ireland and Scotland.