Automatic Account Creation... beware!
As a small business, I've encountered numerous "hacked" PayPal accounts over the past year. These accounts, used to activate a client login, merely dispute the charges one-to-two days later, when the real account-holder finds the charges and stops them. I'd recommend using a system that'll allow you to monitor the Payment Processing and allow you to create the orders with a click of a button, or an "Approved" option, prior to creating everything automatically.
Of course, that's just my opinion, and that's all it's worth...