Martin Ryan,

I entered Oíche Mhaith into a new app that lets you hear what Irish words sound like, and the first example on that site to my ears does indeed sound like ee awa.
I do not know Erse, so cannot argue the point, but perhaps the pronunciation varies around different parts of Ireland.
So in my own version which I have just uploaded, I sing it as ee awa and write it in the annotations as Oíche Mhaith.
I do know however that in Manx, my own country's language, 'good night' is Oie vie which is pronounced ee vie (rhyming with 'eye')

Here is a link to my own version:
Love Is Kind (Including lyrics and chords)