You could do Argyll and Bute, you can do ferry trips, lochs and mountains, not far from Glasgow, then have a couple of days in Edinburgh,and stay In a castle - Dalhousie as mentioned above, Greywalls if you are Rockefeller, Melville.
You will stand a better chance of avoiding the midges on the east coast, and they can absolutely ruin a holiday if they’re bad. Fife is beautiful - you could visit Culross and Falkland for palaces and history, the East Neuk for pretty fishing villages and great beaches, St Andrews, Tentsmuir forest and Dundee. There are castle hotels in the area - Kilconquar (sp), or somewhere like Balbirnie.