You've named the good ones DublinPilot. If you do opt to stay somewhere else, make sure you still go to the Harbour Inn for a meal. It was fantastic last time I visited.
As a note in the margin, Scott, the owner and chef was looking to sell up last time I stayed there, with a view to moving back to the mainland. I don't know if that has now happened or not, but it would be interesting to get a PIREP on whether or not the food has suffered.
If it turns out that you can't find a decent place on Islay, consider the idea of basing yourself in Oban instead. Within 10 minutes or so of Oban is the
Lerags House Hotel. This little gem should fit the bill nicely
2D