I like [name]Sonia[/name]. I think it would be far more refreshing to hear amongst all the [name]Sophia[/name] girls that are around every turn (not that [name]Sophia[/name] isn’t a nice name in its own right, it’s just everyone is recognizing its beauty). I’ve seen this spelling in real life as well as the [name]Sonya[/name]. Can’t see any difficulty in using it on a baby of an Irish background. And [name]Sunny[/name] is very cute.
A suggestion that I have if you want the “Sahn-ya”: [name]Sanya[/name] [نيّة (Arabic)] - Means “brilliant, splendid”. With a nickname like Sani, you could probably still use [name]Sunny[/name] if you wanted.
Good luck 