Pronunciation of Áine varies with area in Ireland, but somewhere between Awn-ya and Arn-ya. It is of course the Irish equivalent of Ann or Anna.

Make sure you teach people how to pronounce it properly if you do use the name; I know an Áine over here in England who accepts that people will pronounce her name Ay-na, which to me is a horrible corruption of a beautiful name.
(And to get the accented Á, try holding down the AltGr key [to the right of space bar on my keyboard] while typing the letter A.)

I love the name Declan too, Jenny. I had a major crush on a Declan many years ago- and no, it's not mudcatter Declan. :0)