Should you wish to venture 'up north', Enniskillen Airport comes highly recommended. You will also benefit from picking up duty free fuel if you flight originated in the free state, though make sure you tell the boys you are coming from and heading back to Southern Ireland! There is a seaplane based there run by Steve Powell one of the best Seaplane pilots in the British Isles and this is definitely worth considering - the Fermanagh waterways are a beautiful part of this island and both beautiful from the air and always beautiful runways!
In any case, you should have a great trip and I hope the weather is on your side; céad mile fáilte!