Kyriaki - keer-e-ah-ki That one is Greek so more straightforward.
The others are Welsh but true Welsh pronunciation and what comes out of English mouths tend to differ a bit. Here's the closest I can get you to Welsh pronunciation but if you see this in use outside of Wales you might get an Anglicised version or even a 'best guess' from parents without a lick of Welsh in their linguistic repetoire.
Aeronwy - eye-RON-wee (in Wales the R is slightly rolled)
Ceinwen - CANE-wen (most English speakers would come up with something like KYN-wen probably)
Esyllt - toughie, just go with AY-silt and if you can say the L with a 'soft' tongue so much the better. In Wales the LL sound is done by placing the tongue as if to say the normal L sound in English but then emitting breath instead of using vocal cords. Like nothing in English at all and even Welsh students have a heck of time with that one so skip it unless you're serious about your Welsh. Esyllt is simply the Welsh form of Isolde so take your clues from that one.