There is a bit of a distance between Galloway and Mull
A wee drive up the west coast to Ayr and get the ferry over to Arran (not been there since I was teeny wee, but it is on the list for when we have a few days to get away) You could even pop over to the Mull of kintyre from Arran. [edit to add - the Arran Ferry leaves from Ardrossan actually]
You should spend a day in Glasgow seeing museums (Glasgow museums are free entry) Kelvingrove Museum and Art Galleries is pretty good, and there is a new museum just opened (riverside museum) that is apparently very good.
Drive from Glasgow up to Loch Lomond, if you take the East Road up to Balmaha (from where Conic Hill is a pleasant climb with gorgeous views) The Oak Tree Inn is to be reccomended for pub grub. You can drive that road as far as Rowerdennan there are some lovely places to swim in the Loch (the west side is too busy/ touristy for my liking).
Near Rowerdennan is Ben Lomond which is a days climb, as far as I know you should be able to wild camp/ park around the area (its a national park and I have only done it in the campsites, of which there are a couple)
That is as far as you can drive on the East side, you'll have to drive back round the bottom and up the West side of the Loch.
At the North West of the Loch You MUST stop in at the Drovers Inn (assuming it hasn't been refurbished) they have the most amazing (moth-eaten) stuffed animals in the foyer and a huge fire to have a dram by.
Not much further North from the top of the Loch is Rannoch Moore which is worth a wander around (if you can get onto the old military/drovers road that is now part of the West Highland Way) most stunning views ever...
I'd not bother too much with a visit to Glen Coe village... it is quite touristy and the massacre thing can get a bit much at times...
Similarly I wouldn't stay in Fort William too long.... if you like distillery tours maybe? You can drive up the Glen (to the foot of Ben Nevis) and take a swim in the waters coming off the mountains....brrrrr.... take a walk on the footpath up the Glen (it is signposted with 'if you walk this way you will die' (or some such) and several people have... so be careful.... because the sight at the end of the footpath, with the waterfall and the mountains and everything is just AMAZING!!
Go out of Fort William towards Mallaig and stop to take in the Glen Finnan Viaduct.... amazing when you see a steam train going over it (we stood at the view point for 2 hours watching them film a Harry Potter sequence, the train going back and forth, back and forth.... with the helicopter flying over to get the right shot... the novelty eventually wore off...lol)
Stop to take in the silver sands of Morar too, again there will be plenty of places to stop or camp.
If you can, take the ferry from Mallaig to Skye.... much more magical than the bridge, but I don't know if it takes cars
....
I'm going to leave it there but I might add more later
All my holidays as a child and young adult were spent visiting family and camping around the Fort William area, I've also walked the West Highland Way.... If I had had a holiday in the past 5 years it would have been back up there again.
Can I also add a plea (not directed at anyone in particular) please do support local business in these area and try to avoid the chains, these small businesses rely on the tourist income and support many more jobs and lively hoods in turn *stands off soapbox* and leave nothing but footprints, take nothing but photos x
. We traveled in Scotland a bit last summer living in the car, which needless to say was rather uncomfortable (but rather MORE comfy than it was for the two months we lived in it in Europe 
) so we're really excited about going away this time with more space! Anyway, we plan to just park up in lay-bys, overnight car parks, anywhere out of the way really. 
