14 days in West/Northwest Ireland

Aloha Anthea. That sounds reasonable. My first trip to Ireland (47 years ago) was not as long, and I was moving a lot more than your plan, though being in my 20's allowed for more movement.. I also didn't mind not knowing where I was going to stay. I spent a full day in Dublin (I came from England, so jet lag was not a problem - jet lag is real, especially for us older guys). I drove clockwise with my first goal being the Ring of Kerry for a couple of nights, then a couple of days to get to Galway and a couple of days around Galway, before taking the train back to Dublin. It sounds like you're planning a more sensible trip and I think it sounds very reasonable. Rick's Ireland tour book is great (I'm going in early April). I recommend getting it - I know I learned a lot and I know Ireland a bit.
Your father lucky to have you as his tour leader! Bon Voyage.
Kevin

Not sure if this is your first trip, and I don't know what you like (music, hiking, views, foodie, museums) but my feedback would include (and understand we travel fast and light, which is not what some prefer):
1) You could hit New Grange on the way to Galway to save a day trip at the end.
2) We love Galway, but you'll run out of things to do in four days. You could head to Connemara as a day trip, but it would be easier on the way to Sligo. Same for Clifden and Westport. Maybe an overnight on Inishmor?
3) Never been to Sligo (will be there in 2026) but we loved Donegal, but three days is a lot of time.
4) Again, three days is a bit much for Dunfanaghy. Doe Castle, Glenveagh NP, the Workhouse, Horn Head, are all nice, but town only has a few bars, scarce music, and little to do.

My itinerary would be something like
Dublin, one night (depending on where you're flying from, going straight to Cavan might be practical)
Cavan or Cong one night (to let you get an early ferry to Inishmore)
Inishmore one night
Galway three nights
Clifden or Westport one night
Sligo 2 nights
Dunfanaghy two nights
Dublin, three nights.