First pay attention to the correct terminology.
- Supersaver ticket: A discounted ticket for a route. Not flexible. You must take the train you selected during booking,
- Saver Day Pass: An all you can eat pass, good on all public transit in the country.
- Point to Point ticket: Normal ticket for a route. Flexible Good for one trip on a train or trains of your choosing along the route.
Supersaver tickets are not a good choice when arriving by air. A saver Day Pass however is a good choice, as it is usually cheaper than a normal ticket if bought sufficiently in advance, and fully flexible
So go to sbb-tickets.cc and see if a Saver Day Pass is available for Aug. 30. Do not wait to long, as these passes get more expensive as the travel date approaches.
For Grindelwald to Lake Como the first question is: Where on lake Como. If you are going to Como town you can just book Grindelwald - Como on sbb-tickets.cc. And here you can save money booking in advance.
Lastly: What are you planning to do in Grindelwald? There are local passes that may be of use, and if you plan to visit the Jungfraujoch get the Half Fare Card. That makes all your transportation cheaper, including the trip from the airport to Grindelwald. The HFC is especially good value if there are children under 16 in your party, as it comes with the family card, giving free travel for yoru children. Even on expensive mountain excursions.