I live in Dublin, which is lovely, especially in the summer. There is plenty to do and see if you're into walking about and looking at buildings and stuff, and a couple of nice but small museums and galleries. You can take day trips from Dublin to walk about in the mountains or by the coast. There's also Newgrange
, which isn't too far away. Eating should be easy enough, I can give you some tips if you want.
Will you be driving?
Outside of Dublin, the West of Ireland is great - Galway and Clare are beautiful. The Burren http://en.wikipedia.org/wiki/The_Burren
is one of my favourite places. Have you seen Father Ted? You can visit the cave they went to (The Ailwee Caves) and his house is around there somewhere too. The Cliffs of Morne are beautiful. Kerry and Cork are lovely too, I haven't spent too much time there, but West Cork is gorgeous.
I haven't spent too much time up north either, but plan on visiting the Giant's Causeway myself at some point. Belfast is a nice place. There's a lovely village called Carlingford on the way up to Belfast from Dublin.
Outside of the big towns, eating options can be limited. I spent a bit of time doing field work in the West, and we pretty much relied on pub grub, which for me meant chips, salad, chips, mabye a toasted tomato sandwich with no butter, but mostly chips. Not terribly healthy! If you're more flexible though, I'm sure it's possible to find better eats!