The problem with busking in Ireland is that there are just so many excellent musicians and there is a lot of free music to be had for those who want to listen (sessions in many of the pubs). I don't think you should count on busking or spur of the moment gigging to pay your way while you're there. If you can get some gigs lined up ahead of time that might help but I think you're far too late if you're hoping to get something for this summer. By all means go over to soak up music and companionship and I'm sure you'll meet lots of nice people, but you'll need to take along enough money to support yourselve on while you're there, and it would be a good idea to do some research (travel guides, etc. to get a realistic idea of how much money you would require. Ireland used to be inexpensive, but unfortunately it isn't anymore.