You can preset group size, pricing, and options in the Registration Options field. 

Start by enabling Group Size Requirements (toggle to yes): 

Set your required group size and price in the group option.

The price is the total price you'd like to charge, not per registrant.

Save and publish your changes. 

Now if a registrant selects the Group option, the form will automatically populate the number of registrants required. 

It will also lock in the option, price, and number of registrants needed to fill out the order.  

FAQ:

Can my users add an additional registrant after choosing a Required Group Size option? No - If an order has a Required Group Size option, they will not be able to add another registrant, even at a different Registration option, to the order.

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