My experience was the same as Donna's.
In retrospect, I would have taken a sack lunch for the day we transferred from Kinsale to Dingle. We stopped at Muckross House for lunch but it was touring time as well and I didn't see everything that interested me. Ditto for Blasket Center. We stopped for coffee in the cafe, did some of the Center, then went back for lunch. In retrospect, I would have skipped coffee, had a quick lunch and spent more time looking around there.
The guide I had never mentioned/suggested grabbing a bag lunch.
This was my 2nd tour so I am more adept now at figuring out where I might need food. If I have a question about timing I will ask the guide a few days ahead if a stop is just for lunch or lunch and touring.