Much of the stuff around Balmoral is good – avoid riding up to the various pyramids and monuments to Victoria’s children and you’ll dodge the steepest and roughest paths.
You can start in Ballater, ride to Polhollick, from where there’s a short push as the old path has been washed away by floods. Then follow the B976 (which is very quiet as it doesn’t really go anywhere) then turn left at Mains of Abergeldie and ride the small road to the distillery.
From the distillery you can do a loop of Balmoral (there’s an obvious loop of forest roads around the hill immediately south of the castle from Easter Balmoral) or if you can handle some hills you can turn south towards Loch Muick on a smooth and well surfaced gravel road. If the hill gets too much, turn left halfway up and descent to Glen Girnock. If you’re having a good time, keep going all the way over into Glen Muick.