Dublin to Galway, then to Dingle and presumably back to Dublin again, all within 3 days? That's a lot of driving and leaves you with little time to actually visit places I would have thought. A better option perhaps would be to base yourself in Galway for the stay (Dublin to Galway will take about 4-5 hours driving and there's a couple of tolls enroute). To the west of Galway there's the Connemara National Park to explore along with some spectacular coastline, you could easily spend a couple of days in that area. Then to the south of Galway there's the Burren, a karst limestone landscape with caves you can visit.
Dingle's quite a distance from Galway and the roads once on the peninsular aren't that great. As spectacular a place as it is I think you're better off leaving it for another trip when you can also include the Killarney National Park and the south-west coast.
I'm staying in Connemara in July for a week, can't wait!