Ireland with my 18yr old son - anything can't miss for that age?

If he is interested in sports you might check and see if there is a soccer, Irish football,hurling or rugby game scheduled while you are there. Normally I do not recommend the Guinness Storehouse but an 18 year old boy would probably enjoy it.

My 15 year old son thought the Guinness tour in Dublin was fun. Also, we had watched "In the Name of the Father" before we left and so both he and my daughter really enjoyed touring Kilmainham jail as they had filmed it there. Otherwise they also liked the Cliffs of Mohr, climbing St. Patrick's mount, hiking the Burren, seeing ruined abbeys, castles, etc. But probably he'll get the biggest kick out of going out legally with his cousins (who I also assume are old enough?). My two went out to a pub with some English friends of ours in the small village where we were staying. And even just drinking Guinness at lunch (which we all did) was a treat, even though they were with their parents. They enjoyed the "drinking like an adult" versus the sneaking out and getting wasted thing.

One other thing - and not sure you can fit this into your itinerary - we wished we had had the time to go to Northern Ireland. My husband's partner went with his 19 year old so and they really enjoyed it. It was just a different feel for them (and they do have Irish roots) to be there as opposed to the Republic of Ireland.

If you're in Dublin on a Sunday, you can watch/participate in pick-up games of soccer, cricket, and hurling for free in Phoenix Park. My 17-year-old niece played soccer with a bunch of boys there. If you're heading to Guinness and/or Kilmainham, it's out that way.

Visit a pub or two.

"One other thing - and not sure you can fit this into your itinerary - we wished we had had the time to go to Northern Ireland. My husband's partner went with his 19 year old so and they really enjoyed it. It was just a different feel for them (and they do have Irish roots) to be there as opposed to the Republic of Ireland." I couldn't agree more. NI is culturally rich in a different way than the Republic. Great suggestion.

Have the cousins check to see if there are any good concerts happening so he can go with them. When I was 17 I saw an amazing rock concert in Croke Park in Dublin which was very fun. Dublin's city center is pretty compact and quite safe to walk around solo. If you're comfortable enough with his maturity level, why not let him wander about on his own for a few hours during the daytime? He can stop off at a pub in Temple Bar and have a pint, shop for souvenirs then grab a takeaway lunch at Marks & Spencer's Food Hall on Grafton St and hang around St Stephens Green or Merrion Square. This gives you time to perhaps see something he may have no interest in.

Thank you all for your replies! My son is a big sports fan (and will begin playing soccer in college come August), but June seems to be the off season for major league sports of any kind (that I could find). We'll be in Cork City over the weekend staying with my father's cousins (in their 70s), but we're hoping my son will be able to hook-up with the grandson's who are 20 and 18. We will definitely do the Guinness and Kilmainham Jail tours. The Cliffs of Mohr and the Burren are on my list because I missed them on my last trip (before my son was born). I will consider the North when planning, but we will only have 7 full days (including the day we arrive at 5:30am), so it will be a very short "sampler" tour - just to wet his whistle (in more ways than one)! :-)