Rosie, Chris and Patrick cycled from Mizen head to Malin head in 6 days to raise money for the VISION 2020 Kano project. Rosie was in charge of the planning, and you might be interested in the itinerary she chose for the team:

Day 0. Sunday, 6th Sept. Be driven to Mizen (near Cork) from Derry by Martina in support car with bike trailer.

Day 1.  Mizen to Killarney.  127 km. Whole day with fantastic scenery.  Second half of day involves two mountain passes. Here’s a few photos of the early part of the trip.
Day 2.  Killarney to Kilrush.  143 km.  Via South pole bar in Annauscaul., Dingle. First half of day through magnificent terrain, second half flatter though.  Ferry from Tarbert to just outside Kilrush accross the mouth of the Shannon.
Day 3.  Kilrush to Athenry. 129km.  Via Cliffs of Moher.  The Burren – lunar landscape.
Day 4.  Athenry to Carrick on Shannon.  104km.  Lakelands.
Day 5.  Carrick on Shannon to Victoria Bridge.  121km.  Via Enniskillen, Castlederg.  A landscape most of you know.  Quiet, rolling countryside for those that don’t.
Day 6.  Victoria Bridge to Malin Head.  85.4km.  The grand finale on Sat 12th Sept. Via Derry and the North Pole bar.  Aim to be at the North Pole bar for 2pm to meet up hopefully with a good crowd of cyclists who’ve done a week of work while we’ve been messing around on our bikes on the high ways and by ways.  Final sprint/limp through Inishowen (by the scenic route, of course) to Bamba’s crown, Malin Head.

Martina has put together a fun video of the event.