If your product price is based on the number of people in the group, this is how we recommend you set up your pricing.
Firstly, set the number of ticket types you have per group. In the image below we have kept it to Adult and Child.
If the pricing for your groups is per person, uncheck the Child box and enter "Per Person" into the Adult Ticket Label field then delete the numbers in the age fields.
You will now set the different group sizes up as options as shown below, you can name the option whatever you want in terms of group size (press + Add Option to add more).
You can then set the Retail rates and optional Minimum and Net rates.
This is how your pricing would be displayed on your product page based on the settings above.