Morning: coffee at Lanesbrew or Cata Coffee, then down to the water for a boat trip with Lough Ree Access for All (book now) or an electric boat tour with Lough Ree Boating & Walking Tours (book a tour). Ask about Inchcleraun and the other islands.
Afternoon: drive 15 minutes east to the Corlea Trackway, then loop back past the ruins of Rathcline Castle (on private land, so view it from the road).
Evening: a tasting at Lough Ree Distillery (book ahead), dinner in town and a walk across the bridge as the sun goes down.