Elizabeth, I think it is impossible to say what your friend would find appropriate, and I'm not trying to be rude. I'm guessing your friend a) doesn't speak Irish, and knows very little about Irish traditional music in Irish or English; b) like many others of Irish ancestry, likely wishes or believes there SHOULD be a body of lovely, happy songs that fit with their personal view of what they want sung at their wedding, and; c) probably isn't really giving much time and attention to the music for the wedding.

Now, if any one of the above is true, there isn't much that can be done for the happy couple, I'm afraid. There just isn't a body of cheesy sorts of "Wind Beneath My Wings" songs in the Irish tradition, no matter how badly some people want there to be that one perfect song for THEIR wedding.

There are many songs with beautiful melodies. Most traditional love songs are pretty dark, stark, and ring true to reality. That is to say, the songs are about arranged marriages, the cursing of arranged marriages, the rake running off after impregnating the girl, and infidelity. Brides are notoriously superstitious about the singing of such sorts of songs at their weddings, regardless of how beautiful they are. They much prefer the illusion that all will be romantic and rosy for them once the ring is on the finger, and on the day, who can blame them?

I don't mean to sound like a downer. It is just that there is a lot of beautiful music that can be used, especially if one looks at religious songs praising Mary and Bridget, that sort of thing. But they have nothing to do with marriage. They are just nice sounding, and vocal arrangements can be done for solo or chorus, that sort of thing. There are many, many wonderful songs, and CDs of Gaelic songs that you could use to come up with something really beautiful. But the subject matter of the songs doesn't have anything to do with love and happiness.