Book offerings with the cart
Choose slots and add-ons, then create one invoice for the whole cart.
Choose a child, listing slot, any available add-ons, and a submitted registration form when one is needed. Add each choice to the cart.
Review the cart and check out once. Hivelee rechecks every slot's deadline, eligibility, form, add-ons, and remaining capacity before creating any booking.
A successful checkout creates one invoice with one line item per booking. If any slot has filled while the cart was open, the entire checkout fails and no cart booking is created; remove or replace the unavailable item and try again.