4 cities in 7 nights would be too much for me, but it's your trip...just remember that a 2 night stay only gives one full day in each place, so every other day is spent packing and unpacking and getting to a new place.
With that in mind I would definitely rent a car if you're going to visit these places in that amount of time.
Waterford to Dingle and Dingle to Waterford will be a long drive.
Travelling times are as follows: reference www.aaireland.ie/routes/
Waterford to Dingle
Total time 4:09
Distance: 161.85 miles
Dingle to Galway
Total time: 4:10
Long journeys. You wont have much time for anything.
This may offend people livining in certain areas but for the common itenerary avoid Dublin and Waterford, generally avoid the east coast.
Fly in and out of Shannon preferably especially if you only have 7 nights.
You can travel to Blarney in Cork, over to Kerry up through Limerick, into West Clare(not to be missed) and up to Galway. From there you are only 1 hour from Shannon for a return flight.
stella, for only 7 nights i would recommend flying in and out of shannon only because there is so much to see in the southwest and what you have planned now is tons of driving....you will spend more time on the road that you will enjoying things......
you could visit galway, bunratty, limerick, killaloe, dingle, killarney....it wouldn't give you much time in any place but it would be doable without so much transporting yourself from one place to the other.....
you could spend your last day and night in bunratty as it is only 15 minutes from shannon airport and is a lovely way to end a trip....besides the castle and the village, there is the creamery restaurant and durty nellies pub and restaurant, both of which are wonderful....then there is a great shopping area across from the castle for buy all kinds of souvenirs.....
hope this helps some......