Congratulatons on booking this trip! I think you will really enjoy it. We were on the Aug. 4 trip, and even though we got very lucky with the weather (very little rain and a couple of really sunny days), I was fine in a long-sleeve shirt and long jeans on all days. On the sunny days, I would also have been fine in a short-sleeved t-shirt, but I wasn't uncomfortable in long sleeves that I could push up. So you might want to bring one or two short-sleeved shirts, but having mostly long sleeves is what I would recommend. I also brought a couple of pair of capri length jeans/pants that I never wore. For shoes, waterproof hikers are a must. I mostly wore those once we got out of Edinburgh (and, in Edinburgh, I wore sneakers). I did wear flats to the dinners, with white jeans or cords and a sweater or nicer top. I did not feel at all underdressed for those events.