Credit cards

Since you are getting euro, does that mean you will be traveling to the Republic of Ireland? If you go into Northern Ireland, they use the G. British Pound. That is likely way more cash than you would use. Many, would recommend waiting until you get to Europe to get your cash. For travel to Europe, I always consider Visa to be my primary card, however, I always bring 3 types of cards-AMEX, Visa, and Mastercard. Every once and a while we get to a country where AMEX is more widely accepted. Portugal and Australia were a couple.

One caveat on the cash. If you are staying at B & Bs, many Irish B & Bs require cash.

If you receive responses from those who've been to Ireland that's of course the advice to follow- but meantime. after widespread travels in many European countries it's been rarely accepted. I take mine for the Delta points and sometimes larger hotels or more costly stores have accepted it, but then it's always a nice surprise.
Sidebar- for years I used Capital One as my alternative to AmEx, but now they are on the Discover network. Great advice (as usual!) from here on the Forum was a Schwab card, fast and easy online despite that I have my credit freeze activated.
Edit: I agree about the cash but would get 1/2 and 1/2 currencies depending on the length of time for each

As noted above, you will likely find few places that want cash only. Credit cards, by card or on your phone, is now the norm. Visa and Mastercard are by far the most accepted. Amex is usually limited to hotels and higher end stores. Discover is not commonly accepted.

Spent two weeks in Ireland last month and Visa or Mastercard was widely accepted. Hotels were the only ones to accept my American Express. I took out 200 euros at a Dublin ATM and that was all I used the entire trip, mainly for tips. For the first time ever, I loaded a Visa card to my Google Wallet on my cell phone and used it for "tap and go" for the majority of my expenses. It was the preferred method of transactions.