When a customer places items in their cart, they will remain there until payment information is provided and the order is completed. Customers who would like to order photos from multiple albums (e.g. parents of multiple children in the same school) can do so by continuing to add items to their cart.
You can also create specific Sibling/Buddy Product Packages for these cases.
Please note: It is currently not possible to purchase photos from multiple jobs (e.g. customers who would like to purchase photos from both a school picture day and a holiday family shoot) within the same order. Please advise these customers to make two separate orders (And perhaps consider providing them with a discount code for their trouble).