Trip to Mull and then your pick of Iona / Staffa / Tobermory
Walk / cycle round Kerrera
Cruachan visitor centre (or climb it)
Sea Kayaking
Sea.fari trip from Easdale to Corryvreckan. Check their website for the best dates for a spring tide
Cruise Loch Etive from Taynuilt
Maybe something on in the Corran Halls depending on your dates. Kevin Bridges booked for 14th and 17th July although both dates could be sold out now.
Explore the general area e.g. Dunollie Castle, McCaig’s Tower, Dunstaffnage Castle, War & Peace Museum, Oban Distillery, Open top bus tour, Falls of Lora
For food try the Seafood Temple, Coast, Ee-Usk, Piazza
Golf? Course in Oban and also Balvicar, Taynuilt, Dalmally