Sounds like no car.. Athenry is reachable by bus or train. Has the Castle (tower house) Visitors Centre (bit pricey perhaps) and Abbey (phone ahead for a personal tour). Celtic Crystal and Connemara Marble and a spot of lunch in Moycullen by bus?

Limerick by bus/train, King Johns is open year round now (as is Bunratty)

There is a fair bit around if you have a car but most would be off the Bus route or a bit of a bind getting too and from.