Leaving in 3 days...is this itinerary doable or too much?

I've put together an itinerary with possible stuff to do, but I'm wondering if it isn't a little too charged. Any help with paring it down and polishing it up would be greatly appreciated!!

Day 1-arrive in Dublin
Day 2 Drive to Megalithic sites (Newgrange, Knowth, Dowth, Loughcrew),
maybe drive through Athlone on our way to Clonmacnoise
(monastic ruins). Continue to Ennis.
Day 3 CLARE Visit the Burren, stay the night in Doolin
Day 4 CLARE hike along the Cliffs of Moher, stay in Doolin
Day 5 GALWAY drive to Galway/Oughterard/Spiddal---Visit Connemara
(+Kylemore Abbey?)---stay in Roundstone.
Day 6 GALWAY Visit the Twelve Bens--stay in Roundstone/Clifden
Day 7 MAYO Drive to Westport (visit Croagh Patrick, Doolough Valley,
and the Ceide Fields) Not sure, but maybe we could drop this day?
Day 8 SLIGO Drive to Sligo town. (Visit Carrowmore megalithic
cemetary and Carrowkeel passage tomb cemetary, Knocknarea Cairn)--stay
in Sligo
Day 9 DONEGAL Drive to Donegal, visit the Glen Gesh Pass,
stay in Glencolumbcille
Day 10 DONEGAL Visit the Slieve League--Stay in Ardara
Day 11 DONEGAL/DUBLIN Drive through Glenveagh National
Park, see the Inishowen Peninsula, pass by the
town of Buncrana--Return to Dublin (This is probably too much for one
day)
Day 12 DUBLIN --Return to U.S.

Thanks in advance to anyone who can provide some (very) last minute help. :)

A bit of a busy schedule, you could do it, but I'm sure you've read on here that the roads are not the fastest.
You mention dropping day 7. Well if your heading north out of Galway, its not to much of a diversion to head along the Doolough pass, the scenery from Delphi to Louisburgh is stunning, and you do get a sense of some of the sad history the area is associated with.
You'll pass Croagh Patrick on the way into Westport - you dont say if you're intending to climb it though. Never been to the Ceide fields so don't know if its a must see.
If you have time in the Sligo area, a boat trip makes for a pleasant afternoon, and you have the added bonus of venturing into County Leitrim, Irelands gem : ) Hargadons is a nice atmospheric place for lunch and a pint or two in Sligo Town.
If you're staying in Ardara, Assarancagh Waterfalls, near Maghera are worth a visit.

"Visit the Twelve Bens" etc. Well you'll either see them or not depending upon if the weather is clear while you are in the area: you don't need to schedule any extra time to "visit" them if seeing views of them is the limit o fyour ambition. If you intend some hill-walking in the 12 Bens, be aware that there are not official footpaths nor signs in the range, which is mostly private land, and that all walking routes over the hills are very rough walking over steep and loose rocky terrain, exposed in places, in places. I would advise buying a book on hill-walking in Ireland, as the rights of way/footpath sitation in Ireland is very unsatisfactory and you need detailed advice on what to do and where to go, as just buying a map isn't enough. There is the "national park" interpretation centre just north of Clifden, where you pay to go in and can walk a short paved path up a little hill. OK with children, or for people who don't really do proper hill-walking.

No logistical problems difficulties climbing Croagh Patrick if that is your aim. Just go to the car park and set off from there. But the path is very eroded and steep on the upper parts - a pile of rocks which move - and it will not be an enjoyable walk if the weather results in the rocks becoming slippery. People do occasionally have really nasty accidents on this path. But I saw a completely blind lady manage it with help from a companion (on a dry day) - I was quite impressed given I nearly ended up on my bum a few times.

Slieve League is also fairly straightforward of access - you just drive to the car park along the scary narrow road and set off up the path. There is some quite exposed, steep, eroded ground, to cover if you intend to go right to the high point. You can arrange it as a circular walk if you have a map, though the routes are a bit indistinct in places, and you just have to set off in the right direction over the land at times.

I think you might find Day 2 a bit much. But after you've done the Boyne valley attractions, you can see how the day is going and drive straight on to Ennis if time is pressing. Cross country from the Boyne, getting to Ennis will be a slow drive. There's nothing much in Athlone, pleasant enough but nothing special. You are right, Day 11 is a bit much. It will talk you about 4 hours or so to drive back to Dublin after you've finished.

I did a very similar holiday myself about 3 years ago, at exactly the same time of year. It worked better to take in the Boyne valley monuments on the way back from Donegal. They are more nearly on the way from Dublin to Donegal than on the way from Dublin to Clare. I would recommend trying to stay more than one day in more places and missing out some of the intermediate stops. My wife says she would have preferred to just visit Connemara and Donegal, and forget the stuff around Sligo/Westport. It was impossible getting accommodation anywhere near Donegal town, but once we headed out to Ardara and beyond there was plenty of availability.

Thanks so much for the quick response! Your input helps a lot, especially concerning the hiking/walking. One of the members of my group had knee surgery a few months ago, I'm afraid she won't be capable of doing any heavy-duty climbing or walking. I don't know why I didn't take that into consideration, I just made a list of "things to see". Now I think I'm going to have to make some major adjustments. Thanks again.

I'd stay two nights in Glencolumbkille or two in Ardara, rather than splitting them--they're not all that far apart. In general I'd say what you have is doable, but if you cut a bit and have fewer one-night stops you're likely to enjoy it more. I've got Ireland photos of the areas around Doolin, Glencolumbkille and Clonmacnoise, among others, in case you're interested.

CK

Definitly doable and well thought out. Enjoy it