If it is sand and sun you are after.....there is plenty of sand at Dornoch beach and if you are lucky with a clear day you will get sunshine too...otherwise put on a good coat and enjoy the walk anyway - you can walk down the beach towards Dornoch and a do a circular route.
Dornoch beach is about a 45 minute drive from Dingwall - use SatNav IV25 3LD for the carpark. Parking is free and there are toilet facilities. The sand is so fine and the water incredibly clear, so a good place for a swim.
The town of Dornoch has some lovely small independent shops, coffee and antique shops. Parking around the town is also free.