Maggie,
 
I can tell you are getting very excited and that your countdown has begun. I usually take a small amount of traveler's checks in US dollars as a back up in the case of extreme emergency. Otherwise I charge everything I can on my credit card. After that I use my ATM card for cash at Irish banks. They do not charge a fee for their use. Your bank may add charges. I get a certain number of "out of network transactions" free per month and actually use my credit union ATM as it has less fees than my bank.
 
I wait till I get to Ireland to get cash. On the odd occasion that the airport ATM is out of cash, there are plenty of them available all over Ireland. 

In Ireland you use euros not US dollars. If you wanted to exchange US cash you would have to go into a bank and would be charged a fee. Same with traveler's checks. Be sure to re-read my Money page and Tips & Tricks.

Michele