I did exactly what you are thinking about in early July this year. Drove from Cornwall to Port Appin (Linnhe Marina) then headed past Tobermory, round the top of Mull and from there it is a very short trip to the Isle of Coll & Tiree. Spent a glorious week in and around the islands. Wild camping every night except one when a storm was due to blow in and we checked into the excelent Coll Hotel, which wasnt that much more expensive than the Coll Bunkhouse 100 yds away. The Fisherman there let us moor upto the quay so had plenty of shelter too.
Camping was fantastic, we got really fussy about our sites, wanting a very sheltered bay to anchor in, with a lovely sandy beach, and just at the end of the beach a grassy knoll to pitch our tent on. Its quite a demanding criteria, but every campsite came upto scratch, the like of which is very hard to find down here in the southwest. I can give you some co-ordinates if you want, but look on google earth and you will see some wonderful beaches on the islands. We would often moor the rib 1 hr before HW the it would dry out overnight on the soft sand and be ready for us the next morning.
Of course we kept a wary eye on the weather forecast so we never got stuck on a lee shore but ended up moving round the islands finding these campsite beatifully sheltered till the wind moved, the we would shift campsite.
One of the best sites was on the very NE tip of Coll looking directly at the tiny island of Eilean Mor. From our grassy pitch we had a 270 degree sea view from Mull past Ardnamurchan Point to Rum & Skye in the distance. We ended up loving this area some much we didnt go any further. Also big bonus no midges.
They tell me Tiree is the sunniest place in the UK & the windyest.
Here is a link to a video my did the trip. Scotland by Rib 2015