Sorry, re-read your request.
Use the same process as above only reverse the source and target companies. Create the order in the Parent Co, then bring in all the items on the order either as * items or as miscellaneous items so you can avoid maintaining any inventory in Web Co. (This avoids the need for a PO in Web Co.) You can still make all the sales in the Parent company be to Web Co as the customer with shipping addresses as the end customer. However, you will have to maintain two sets of invoice formats and two sets of packing slips unless you add logic to your forms to change the header info dynamically based upon the customer ID. If the customer is Web Co, use format B. If the customer is not Web Co, use format A. This still won't get you around the name on the credit card transaction on the customers CC statement. The only way I can see around that is to bill the card from the Web Company instead. (On the plus side, this will negate the multi-format invoice issue.