I am off to Ireland from the 20-28th of September and here is the plan.

Day 1: Mayo (staying in a B&B in Westport)
Days 2-3: Donegal town with side trip to Glencolumbkille
Day 4: Roscommon (boyfriend wants to visit the Great Famine Museum)
Days 5 and 6: Galway (will be there for one day of the Galway Oyster Festival)
Day 7: Shannon
Day 8: Departure from Shannon airport in the morning

Does this sound reasonable?

This does indeed sound reasonable and quite doable; a good plan without a bunch of traveling crammed in.

Have a great time! You will enjoy Donegal a lot.

Wendy

Thanks so much for your feedback. I am glad to hear that it's a reasonable itinerary. I am looking forward to Donegal the most.

Check out the Quays Pub in Galway. We heard some of the best music of our trip there!

I think I'd cut out the night in Roscommon and add a night to Donegal or Galway. We did a day trip from Galway to the Famine Museum. Since you're looking forward to Donegal the most, maybe this would give you a little extra time up there.
You'll want to have reservations in Galway if you're there during the Oyster Festival.

Day 7 in Shannon? - Nothing happening there. Check out Limerick for the last night (20 mins from Shannon). Home of Angelas Ashes and some great pubs and nite clubs. We stayed in The Jurys Inn (middle of town) about €69 by booking on web Jurysdoyle.com or .ie.