The rule that saves the trip
Old Ireland is on hills, because that is where you built things when people were trying to take them from you. Georgian and Victorian Ireland is on the flat, because that is where you built things when you had money and no fear. The accessible version of this country is overwhelmingly the second one, plus every national park path laid in the last twenty years.
That is not a consolation prize. Killarney's lakeside paths are the best hours in the whole itinerary, chair or no chair, and I would put Muckross above the Rock of Cashel on any list.
Killarney National Park, the best of it
This is the reason the seven day route ends in Kerry. Muckross House sits in gardens with sealed and compacted paths that run all the way to the lake shore, with the mountains rising directly across the water. Accessible parking at the house, accessible toilets at the house and the garden restaurant, and a genuinely level route between the two.
Knockreer, entered from the town side, gives you a three kilometre paved circuit with the Reeks opening in front of you and Killarney's main street five minutes behind. Torc Waterfall is reachable to the lower viewing platform with a push on a short pull, and everything above that platform is stone steps.
The Gap of Dunloe, which every itinerary in the world recommends, does not work. Rough single track, potholes, sustained climbs. Take the lakeside path instead and book an accessible jaunting car if you want the horse and the guide, arranged in advance rather than at the rank.
The Cliffs of Moher, told straight
The visitor centre is built into the hillside and is fully accessible, with lift access, accessible parking close in, accessible toilets, and paved terraces that reach the two best viewpoints. That part is genuinely good and worth the trip.
The famous coastal walk, the one in every photograph, is grass, mud and uneven flagstone along an unfenced cliff edge. It is not accessible and it is not a place to improvise. Do the terraces, take the photograph everyone takes, and give the saved hours back to Kerry.
Dublin and Kilkenny, attraction by attraction
The Guinness Storehouse is one of the most reliably accessible visits in Dublin: seven floors, all lift served, wide routes, accessible toilets on multiple levels, and a Gravity Bar view you reach without a step. Trinity College and the Book of Kells has step free access via a designated route rather than the main archway, and you must ask, because the obvious way in is cobbled and stepped.
Kilkenny Castle works from the parkland side. The grounds are sealed, the rose garden is level, and a lift reaches most of the interior. Staff will tell you exactly which rooms it does not reach, which is the kind of honesty that makes planning possible.
The Rock of Cashel is the hard one. There is limited vehicle access up to the site and helpful staff, but the medieval fabric inside is worn uneven stone with thresholds throughout. Call before you drive.
Booking and the small advantages
Most Irish attractions admit a companion or personal assistant free of charge with a paying disabled visitor. It is rarely advertised on the website. Ask at the desk or mention it when you book by phone and it is applied without argument.
Book timed entry everywhere it exists, not for the queue but for the gradient. Standing, or sitting, on a sloped forecourt in Irish weather for forty minutes is the part of a day that ends it early.