Is 5 full days enough time to explore the Oban area & 3 or 4 of the islands? Thanks!
I think that is plenty of time, and would add that most folks don't spend that much time there if at all.
You can do Iona, Mull and Staffa in a one day tour.
You don't mention which islands you are wanting to go to.
I applaud you for not rushing! Not sure how large an area you mean by "the Oban area," but on the mainland within an hour of Oban there are some pretty cool things to see. One that comes to mind is the Ben Cruachan "Hollow Mountain" hydropower station & visitor centre. It may sound boring, but it's actually fascinating.
We spent 3 nights and I would have loved to spend 5. You will have plenty to do.
I loved Oban. It's great for bird and wildlife watchers like me. Not so great for city slicker types. Take a compact pair of binoculars. Many wildlife boat trips. You can find them online. Gordon Grant Puffin trips. Trips to Iona. Seal watching trips. Many of these day trips go to a couple of islands. Take a backpack with food and drink when going out on the boats with other day supplies.