Hi Shilpi,
If you want more flexibility in terms of options and timings, do consider travelling from Delhi to Bangalore or Chennai and then going on a road trip to Pondicherry. The road journey is impeccable and whether you choose to rent a vehicle or travel by a bus, you will have a good time. Pondicherry is only about 3 hours away from Chennai and around 6 and a half hours from Bangalore (overnight trip). Have a great trip!