Carlingford adventure centre used to be a good spot. Not sure what its like now or how much it costs though. Beautiful part of the world if you were to go.
There is a place in county wicklow, I have added the link, I don't know much about this place, I stayed there in the rented house's over the xmas period and saw the team building area whilst out walking.
If you want a successful team building day I would stay away from packaged "fun days". I would bring in a team building/leadership consultant in to design a specific package. They will talk to you and find out about your business and some of the challenges you face. They will design a day that is not only fun but you will be able to target specific business issues and make possitive changes. You will find they are not that expensive.
I am a ex consultant with military experience so can offer free advice by PM/mail if you would like. Just to clarify I dont want to sell anything as I have a new career now.
I brought a crowd there some time ago and fun generated by the whole craic really did change the way the group interacted. I always find the "them and us" attitude is harder to maintain once a group have been on a day out like this.