I'm prolly a little late with this info (Just joined the group)

But The Great Southern Hotel chain in Ireland do give airline discounts.

Great Southern Hotel

I stayed at the one at the SNN airport last March on my own and several times before when passing through on company business. The one in Shannon is quite nice and the staff was very friendly.

I suggest you visit the website and find the local number for the one you are planning on staying with. Then call them directly and inquire about an "airline staff discount".

As far as rental cars, I picked one up at the SNN airport at the Alamo/National counter and I think they offered a discount as well. I'm not sure on that. But the rates were lower than what I expected. You can book the cars online before you leave. So you can have an idea of costs.

As for driving in Ireland, I picked up an International Drivers License from AAA in Orlando before I left.

Driving around Ireland is the only way to go in my opinion. You can get off the beaten path and explore.

Hope this helps...