Under Ticket Type, choose Adult from the dropdown. The price updates to $20.

Set the Quantity to the number of adult tickets you need.

Click Add to Cart.

Now go back to the same ticket product (click it again, or click "Continue shopping" from the cart).

Under Ticket Type, choose Child. The price updates to $10.

Set the Quantity to the number of child tickets you need, and click Add to Cart.

Open the Cart (shopping cart icon at top right) and confirm all tickets are In the cart.

Click Checkout, enter your name, email, and payment details, and click Pay.

You'll get an emailed order confirmation — that's your receipt and proof of registration.