As a follow-up, I would highly recommend the Fiddler's Sons ceilidh in Poole's Corner on Thursdays. In addition to their own talents, they are bringing in good acts for the second set. Get there early because the locals LOVE this one: it's a big hall, but it was standing-room-only 20 minutes before showtime.
I was actually a bit disappointed by the ceilidh at Orwell Corner. It was culturally interesting (they tried to recreate a bit of the PEI "house party" atmosphere, with audience participation), but the acts were not top-notch. Different from my previous visits.
The oddest thing about the celidhs I saw was how they attracted mostly folks over 60 -- and many of those were American. Relatively few younger people in the audience. Are young people on PEI not interested in local "roots" music? For example, the Fiddler's Sons played with the Grass Mountain Hobos. Nobody would call that bad "old people's music." But that's who showed up for their performance in Poole's Corner. It would be a shame if this music "died off" because younger people are uninterested.