Hi Robin,
It'd be my sincere pleasure to help make sure your trip starts off on the right foot!
Assuming it takes a couple hours to get out of the airport and sorted, I think the
Lemon Jelly Café might be just be open and it's one of my favourite spots to have morning tea. It's a little cafe about a ten minute drive from your hotel, but it does open at 8:45 am on Sundays.
That might be just a wee bit late, though, so I tried to find a spot that opens a bit earlier.
The Taste Food Company is a five minute drive from your hotel and they're open at 7:00 am on Sunday, which might just be perfect. A third option would be
Keoghs Cafe, which opens its doors at 6 am sharp and they're about a seven minute drive from where you're staying. That said, I've never popped by these spots before, personally.
I do hope this gives you a few options to choose from!
Do you mind if I ask what you have planned after popping by the Book of Kells? I'd be just delighted to hear more about your plans or offer any advice, if you need to fill out your itinerary just a wee bit.