Welcome to the forum. If you give us some info about where you will be traveling in Ireland we can recommend some beaches along your route. With a coastline of about 2,000 miles there are many, many choices.
What are you looking for in a beach? Surfing, walking, swimming, sunbathing, scenery? Is your itinerary being planned around beaches? If so, how much time do you have in Ireland? Whatever other info you can tell us will help narrow down your choices.