Hello Xearoolluequ27
Booking a Supersaver’s ticket when arriving from the airport is generally advised against, as it forces you to take excactly the chosen connection. If you are early, you have to wait and if you are late, you have to buy a new ticket. Buy a regular point-to-point ticket in that case.
When travelling with a Saver’s daypass, you can take any train you like.
As you are travelling as a group, you technically have to reserve space for your group. Then, you can also buy slightly discounted group tickets but all of these is also forcing you to take a specific train.
In your place, I would compare Saver’s daypasses and regular point-to-point tickets and then chose the cheaper and simply travel as 12 individuals. Then you in the worst case can’t sit all together, but its much easier and a group of 12 is not going to cause overcrowding anyways.