First, congratulations on 40 years.... I admire your dedication and commitment to your marriage and each other

Second.. Oh my gosh, you have no idea no envious I am

I loved Ireland!!!
I went to Ireland about 10 years ago and spent a week there. My college roommate is married to an Irishman and they live in Dublin. I was lucky and the weather was just wonderful, not too much rain etc. It is just gorgeous and I would go back in a heartbeat.
Funny, my visit with them was just about as you have in mind. I stayed in Dublin with them a couple days and while they were at work, I explored on my own and took the train down the coast to Bray, walked around Dublin etc. That was fun. We drove down south one day and then drove through the middle of the country, stayed with friends of theirs at a farm (amazing experience) and then went to Galway.
I can't tell you how much I would love to go back. I didn't drive myself, which was a luxury. I think if the designated driver has decent skills of concentration and isn't too easily distracted it would be ok. Once you're out of the city it's not busy and you could stop often so the driver could have a look without having to focus 100% on the road. Driving through the center of the country was so cool. It is exactly like you imagine it, we even had to stop for sheep being herded in huge flocks.
I LOVE history so I could have stayed a month and been happy. My only thought for you is do you really want to stay so many nights in Dublin? When I was there, I wanted to go further down the east coast to the south of the country and it was really too far just for a day trip (at least it seemed that way at the time) Be sure you map your planned day trips out carefully to make sure you don't feel like you're missing out by spending time driving back and forth to Dublin.
I loved visiting the historic ruins (just trying to wrap my arms around the idea of how old that country is blows my mind). You have to visit different pubs, the live music is fabulous even in places in the country there is music. Prepare everyone to be adventurous with food, it is different. My favorite was fish and chips in Dublin believe it or not. We ate it out of paper bags on the beach and it is large in my memory. The architecture is incredible, so different than what we have here, although I've never been to New England (that is on my to-do list

) so maybe it will not seem so foreign to you.
OH, I'm so, so jealous.... Please, please, please, promise to post photos here so I can see. I will talk to my friend (they are still in Dublin) and see if she has any suggestions, when are you thinking of going? I think you might try posting this on the UK section of GRF and see if more people there besides AnneF would have ideas for you. Keep me posted

Kristy