One suggestion: Go north. We found that the crowds began at Galway when last toured and that Mayo was equally spectacular and far less travelled. Achill Island in particular was worth a visit, though there is really not much there to put it on a map, just an incredible coastline, a few abandoned villages, lots of sheep and wonderful people. The Mweelrea Mtns, and Dhulough Pass (the road number we took is R335) knocked my socks off on a day when the light and the air were playing with the mountains. I would suggest Clifden as well, but the inland route, and the Twelve Pins through Joyce's Country is an attractive alternative.
Galway itself, my favorite spot from the 70's, has grown up into a pretty big place, with all the pains that come from growing up. Go north to say hi to Croagh Patrick, where the saint is said to have stood to banish the snakes, stay in the beautiful but touristy Westport Quay and idle along Newport bay to Achill. You'll never forget it. If you go south, you might look in at Kilkee, a smallish resort town just north of the Shannon and a great place to walk the cliffs.
I found little choice in film in most places in Ireland. and few places that would do more than the usual one-hour processing outside of Dublin, but then, I admit I didn't look too hard.
Above all, have fun. Ireland is magical in mid-summer, rain coat or no.