We go to Scotland a fair bit with dc (now 5 and 9)
Arran - lovely tiny island can drive round the whole thing in 2 hours. Nice beach (Pirnmill). Quiet.
Stonehaven- great playarea beach fish and chips. Outdoor pool (saltwater). Dunnotar Castle is fab. Close enough to Aberdeen if you want cinema or shops.
Newtonmore - highlands so stunning scenery. Highland Wildlife Park and Landmark Park both excellent.
Edinburgh - great city break. Camera Obscura and the underground city both excellent activities.