That will be a fine loop! Call me biased, but you guys cant really go wrong anywhere in the Highlands, particularly the far north. I love it up there. I actually have a business trip to the UK mid-August, so I'm tacking on a week in Scotland after it. This is making me want to come up with some kind of driving loop myself.
I just hope the potential LHR/BA strike on 23/24 Aug doesnt force me to drive up from London!