Raemoir House Hotel could be fun for cycling – you can pretty much head out the back of the hotel and you’re onto the Hill of Fare – some great tracks around there. Though, that might not help much if you’re just there for the wedding (might be missed if you pop out for a ride). If you’re staying at or near the hotel, you’re about 5 mins drive (or an easy cycle) from some excellent tracks..
See: Hill of Fare
or a variation on it: Strava link
Or Scolty has a huge range of trails and it just the other side of Banchory: Scolty trails
Aberdeen accommodation can be very expensive and generally you don’t get a lot for your money. Hotels in the town seem to be geared towards folks on oil industry expense accounts and there’s generally a lack of supply and too much demand –> expensive. Though this may change if the horror stories about the state of North Sea oil are to be believed.