We did it plus a lot more back in April. Started 21st April, ended 23rd May. Very little traffic, motorhomes a few, everyone waving. We started down at Culzean, onto Loch Lomond, then through Glencoe , over to Skye, up to Inverewe, onto Durness, along to Dunnet Bay, popped to John O'Groats, down to Brora, then Rosemarkie, down through Pitlochry and Aviemore to Melrose before returning over the border. Most amazing scenery. We live in North Wales and think that is good but Scotland scenery is something else. No midges either . I certainly wouldn't go during June/July/August as too busy from what I've read but any other time fine.
We only stayed on club sites (except one, Sango Sands and only because the clubs don't have sites that far up) , only booked 4 beforehand in case we wanted to linger anywhere but had no problems getting pitches. We covered 2050 miles and stayed at 14 sites including ones on the way from home and back. Absolutely loved everything about it.