For now, it is not possible to acquire multiple tickets. The app is only valid for the main passenger.
For your children/grandchildren
If your child/grandchild is under 16, you can get a Junior Travelcard or a Children's Co-Travelcard. With one of this card, which costs CHF 30.00 per year, your child/grandchild will be able to travel free of charge, when they are accompanied by an adult with a valid ticket.
For your dog
There are a few options to purchase a pass for your dog.
For your bike
You can get a year pass or a day pass to travel with your bike. Day Pass and Year Pass exist.