Itinerary thoughts?

It looks like a lovely trip.

I’m not sure I would have prioritised Arran albeit it’s a nice island, especially if you are also going to Mull and Iona.
The drive up to Oban is very scenic, taking you up Loch Fyne via Lochgilphead.Carnasserie Castle and Kilmartin may be of interest.The Loch Melfort hotel would make for a lovely stop, a gem of a place with beautiful views.It does lunch/cakes /coffee etc. Arduaine Garden next door wil be past its best however by autumn.

You then plan to drive north of Oban to the Corran ferry.Glencoe is a short detour on route but you have some hard driving that day so it might be a detour too far.
Ardnamurchan is wonderful but the driving beyond Strontian is winding single track with few long sightlines albeit through beautiful scenery.It can easily take 2 hours out to Kilchoan without stops plus you are planning two 5 mile detours (unfortunately off different branch roads) which will add some time.That said, Sanna is just glorious (and weather will be a factor too), white sand beaches and normally only a few people about.The Lighthouse is a great sight/site too so both well worth it.

We’ve had 3 nights on Iona, it’s a delightful island.Don’t miss a walk out to the North End beaches and possibly a wee scoot up Dun I, the island’s tiny hill, for fantastic 360 degree views of mountains, the ocean and islands.

If you sail back via Oban, then Glencoe is again possible albeit by driving north again. Or else reverse your Ardnamurchan trip and come off Mull via Ardnamurchan which then makes going through Glencoe the most obvious route to Loch Lomond. It’s a stunner of a drive to Loch Lomond from there.You would arrive on Mull initially via the Oban ferry - the loveliest crossing as it turns out.

Thank you @scotlandmac
If we dropped one night Arran, we'd have four nights prior to Iona arrival.

How best to spend?
Mapped out the driving and seems arriving mull via Tobermory and leaving via Craignure involves the least driving
so....
Arran 1 night
Lochranza ferry to Oban 1 night, stay 2 nights? Stay somewhere along the route to Kilchoan? We'd prefer two nights wherever
Tobermory / mull 2 nights
iona 3 nights
return via Craignure with a bit of a back track thru Glencoe to Loch Lomond

Seems the only wild card on this is where best to spend the 2 nights between Arran and Mull

You're flying into Glasgow? OK. Not sure why you are staying there 2 or 3 nights if you're planning day trips to "Edinburgh, Stirling, etc." I appreciate not wanting to stay in Edinburgh in August, but I don't see you getting much from a day trip. The crowds will still be there on a day trip. I would do the Kelpies and Falkirk instead. Either leave Edinburgh for another trip or return at the end of the trip?

Day trips are all up in the air and will depend on the day, Glasgow is probably 2 nights only. We're ending in England so it's at the start or nothing.

There are so many options - what I’m not sure about are the interests of your party? That can help suggest another possible base.

For example, if after Oban, you detoured in to Glencoe , you could spend a fair amount of time enjoying the area, enjoying one or two easy strolls, perhaps a drive down Glen Etive, seeing something of Rannoch Moor.Going up the chairlift for fab views.You could also do even part of the drive round to Kinlochleven which is glorious.Then head across on the Corran ferry and drive for 12 miles or so (good fast bit of road, lovely drive) to, say, Kilcamb Lodge which is a gem of a small hotel and stay there the night.It depends on your budget of course as its got a bit pricey though there are other places to stay on the peninsula.But that would also break up the drive out to Sanna, the Lighthouse and Kilchoan for the ferry.It also depends whether you are ok with 1 night stops.
That then allows you to leave Mull from Oban and not drive all the way up the same road to Glencoe.Not that it’s a major hardship! But you have pretty Inveraray and Loch Fyne to see , new scenery so to speak.

I spent three nights on the Isle of Arran and four nights on the Isle of Mull. I loved both of them, but I loved Mull much more. I would definitely spend more than two nights on Mull if possible, especially if you are using some of those days to take day trips to Iona and so on.

@scotlandmac thanks, but no new places LOL !!! Not big hikers, maybe short scenic strolls. Just experience landscape and culture.

I think i am narrowing it down for this portion, at least until I change my mind tomorrow:
Arran 1 night

This is where i Get stuck:
(1) Lochranza to Oban in the am, then head to Glencoe in the afternoon, and stay somewhere near there/Fort William? Is that a doable route, I know it's a bit longer but we have a lot of slow time coming up after that. Can or should Glencoe Valley just be done as an out and back? Otherwise not sure how to link it up
Glencoe or Fort William ish or surrounds 1 night

Or, (2) what about approaching Glenco anti clockwise on the A83 - A85- A82, i.e. Lochranza to Bridge of Orchy area? Is Glencoe still a good drive from that direction? Continue on and one night in Glencoe or Fort Wlliam or.. Seems that cleans up the flow a bit and then head to Kilchoan

From there I think better suited to get to Kilchoan and across to Tobermory then we just want to slow way down, to a stop
Mull - 3 nights
Iona - 3 nights
Return via Craignure-Oban to Loch Lomond

Seems less backtracking on that route
Any recommendations in the Glencoe area for a night? Looking more for an inn or quaint b&b environment, more unique the better, not a hotel and not fancy as we won't have clothes for dinner :p