I see you made a list of places to go on the Beara Peninsula.
Dursey Island: Yes, absolutely. Bere Island: Yes, absolutely.
You listed Kilcatherine as well. If you go, you could consider a stop at the HAG OF BEARA. It's an odd shaped piece of rock sticking out from the rest of the rock, see image below. People leave offerings such as coins and belongings - on the image a red necklace can be seen. Legend has it that it's Cailleach Beara who is waiting on her husband, Manannan, God of the Sea.
Regarding Dursey Island, be sure to stay at a B & B or likewise within a reasonable distance from the cable car. 3 times in the past I've made the mistake of getting up, enjoying breakfast and be 10 minutes too late for the last cable car departure before lunch break! If you take the cable car AFTER lunch, you won't have enough time to walk to the other end of Dursey Island to see the rocks, the Calf and the Bull, before the last cable car returns to the main land. Now, things may have changed since I was there, I just want you to be aware of the timetable.