For full information about touristic and sightseeing options in Stellenbosch, consult http://www.stellenbosch.travel/.
There are numerous walking tours available in Stellenbosch and environment. See http://www.stellenbosch.travel/route-360what-to-do/trips-tours.
Since many tours leave every day there is no need to book in advance. Select tours are available in German and French (apart from the normal English tours); it is advisable to book those in advance by contacting email@example.com.