Critique my Ireland itinerary

You're right, this is busy. Probably unrealistically so at points. You'll have a car it sounds like, which certainly helps. However, travel times are not always easy in Ireland (especially by car), and driving yourself the 90 minutes or so to Longford on the same day you arrive into Dublin is probably not a good idea just from a safety standpoint as jetlag is real and for most Americans there is some adjustment to driving on the other side of the road that requires extra concentration at first even if you've done it before.

As hard as it is, I think it might make sense to drop portions of your itinerary such as Achill Island in addition to a one-night stay in Westport, or trim the list of hopeful spots for Day 10-11 and add an extra night in Kinsale or Killarney to use as a home base for the nearby areas.

For example, I liked Killarney as a convenient stop (I am aware that Rick Steves disapproves) and the drive from Dingle to Killarney is certainly manageable by itself, but combined with Killarney NP and Muckross House and Muckross Farms that's makes for a very busy one night stay to say the least. You won't drive and see all that in a day and still get on to Kinsale for the next day without running yourself ragged.

One day is too short to do Dublin justice - but I actually like that idea. I'd take another day in Kerry over a day in Dublin myself.

That's just one person's opinion however. In any case, Ireland is a joy to visit, wherever you end up you really can't go wrong.

I totally understand your wish to see as much as you can on your only visit to Ireland. When we took our first trip in 2012 (coincidentally also the last two weeks of September) we also felt it would be our only shot at seeing everything. We started with three nights in Dublin, which I would recommend if you aren't under time pressure to get to Longford. It gives you time to get over jet lag and you won't need to drive right away. After a couple of days touring Dublin you can take a cab or bus back to the airport to pick up your car.

For the rest of our trip we did three two-nighters (Belfast, Dingle and Kinsale) and all the rest of our stays were one night only. We managed to cover the entire perimeter of the island but just did not have time to see everything--no Ring of Kerry, no Muckross House, no Aran Islands. We were also on the road a lot and I know that we missed a lot of opportunities to see some of the beautiful scenery and quaint towns that you are looking for. Happily we were able to return to Ireland several years later so we did get to see those things but also came to realize that our first trip had been way too rushed. If I were you I would eliminate some things, hard as that may be, so that you have time to enjoy the things that matter most to you. Everyone on the forum has a different idea of what to include and what to eliminate so it's hard to give really helpful advice. I personally would probably skip Killarney and thus Muckross House--too many people and terrible traffic (though I did enjoy the house tour and the Park is lovely). We were also a bit underwhelmed by the Cliffs of Moher. There are spots along the Ring of Kerry that are just as spectacular and are way less crowded. And unless you have a clear day, stopping at COM really isn't worth the time. We didn't stop at the Bunratty Folk Park, based partly on what others on the forum have said about it--some loved it and some didn't but it wasn't what we were looking for. We did very much enjoy Westport (wonderful music at Matt Molloy's), Dingle and Kinsale (great food). We also loved our trip to Inishmore but be aware that sometimes the weather keeps the ferry from making the trip--it's good to have a backup plan for that day.

Ireland is beautiful and the people are the best. You're bound to have a good time whatever you decide--but give yourself time to enjoy it. You won't be sorry.