There's no need to dispose of the charger that you get with your iPad in the US. It will work just fine. If you're going to use it permanently in Ireland and don't want to always be using a travel adaptor, you'll find the 'plug part' of the iPad charger just slides out to reveal an international standard, two-pin, IEC socket into which you'll be able to plug an two-pin IEC cable - you'll almost certainly have some already, it's the small two-pin adaptor that is often at the end of a mains cable that's used to connect the mains to radios, TVs, CD players, HiFi systems etc. No need to change the charger.
Tim