Once you have choosen the appropriate checkout option you will need to click "Add to Cart" This will take you to a secure PayPal transaction. You DO NOT have to have a PayPal account to do this as you can use your debit/credit card. Once at the checkout site, you can change the quantity of each registration.
To add another option to your PayPal checkout simply go back to this page, and add the option. This should keep all changes made in PayPal. Once you are ready to checkout, if using a card, click "Check Out" on the checkout page. This will take you to your standard checkout information screen. Fill out all of your information but no need to fill out your email or password at the bottom of the page.