Using eCart for Room Service

I would like to set up a system for guests to be able to add room service items to a database using eCart for calculating prices (variable quantities), and pay for it all once they checkout, which may be a week or 14 days later.

The first step is easy - create a normal eCart, then instead of checkout I insert the items into the database on cart.php submission. Each item is stored with a unique GuestID which is created when they log in (session).

What I need to be able to do is to get this information into a secondary (non-editable) eCart basket/cart page to allow them to pay when they checkout.

I can get the relevant items onto a page using a recordset and the GuestID parameter, but I am not sure how I can then generate the checkout for the total amount. I was thinking that I could create a second eCart Object, but I am not sure how to populate from items stored in database, rather than the live eCart session.

Maybe there is a way to just display the items using a standard recordset, then use a PayPal express checkout button with the total amount?

Any help/suggestions would be appreciated.

Thanks.