How to plan a surprise trip to Ireland for my Mom?

I take it you're planning on sticking to the West, or at least outside of Dublin - I would recommend NOT having a car in Dublin city, as parking costs are extortionate, and not parking in the right place would be even more expensive. You could give your mother mock tickets first - nowadays these are usually e-mailed to the buyer if you buy online (which is a lot cheaper than going through a travel agent), just do these in the form of a voucher that says 'You are going to Ireland on [date] for [how long], etc.' I would also suggest looking into fly-drive options, which would mean that you get your car hire and the flight as a package. For accommodation, look at www.hostelworld.com (don't let the name fool you, they do all kinds of accommodation), www.familyhomes.ie and www.discoverireland.ie. Now, about renting a car: you need to be prepared for the cost of fuelling the thing. Currently a litre of unleaded petrol is about €1.30, multiply that by 3.5 and you get the cost of a gallon. You can pay by credit card at most places, be sure to ask first if they accept these. And also, Ireland might be a small country, but you can't do Galway in the morning and Cork in the afternoon, given the state of the roads, it will take you the best part of the day to get from Galway to Cork (you'll want to stop in a few places along the way anyway) and then the fun begins in Cork because if you don't know the street system, or don't have a GPS, it's really confusing. When you rent your car, ask for them to provide you with one if you don't have one of your own. And if you are getting one of your own, make sure you have downloaded the updated version of Ireland, as this prove to be very very useful to you. And there are parking charges in every town now, so when booking your accommodation, ask them if they have their own car park. Most do. Eating out can also be pricy, so I suggest checking out pubs for food, rather than restaurants. Many pubs do great meals at a better rate, plus you are already in place for the music sessions. And tell your mother to read the small print on her ticket, as there are weight restrictions for luggage, I believe the airlines allow 20 kilos for each person, but many B&Bs could do a load of laundry for you, or point you in the direction of the nearest laundromat.