Autos can be hired in Kanchipuram and they will take you to the main temples in kanchipuram. The Auto temple trip will take about 3 hours i think and also the time for trip will depend on time one spends in each temple. Temples are main attractions in Kanchipuram.
1) visit kamakshi temple
2) hire auto for ekambareswarar temple/ visit temple
3) the saravanabhavan is the best option for food ( not far from the bus stand )
If you have more time the varadaraja perumal Temple and the kailasanathar temple. But not possible to do all this in 2 hrs