If they are paying the bill you might want them to order it under their email. Each parent would need their own email address of course, they should be able to use the same form of payment for both.
If you are handling the billing it might be a little more difficult because of the 2FA and the way it is set up. But you can have the SIM(s) sent out to you or them early as long as you activate them within 30 days.
