This response might be a bit late, but you can just capitalize the first word, as you did in your question. In English, you could capitalize all the words (Always In Our Hearts), but that’s a bit more complicated in Irish – gConaí and gCroíthe are straightforward enough (don’t capitalize the urú), but inár is a compound of “i” and “ár”, and I’m not sure if “InÁr” would be appropriate, or whether you would stick with “Inár”.
But I would also suggest that “go deo” is probably more common than “i gcónaí” in this type of phrase – “Inár gcróithe go deo”.