I don't see an easy way to solve the "PCI DSS problem".
Or you do the full monty or you use a third party company that do it.
I have a Tiki23 using tracker forms (order, subscription) with an URL to a third party company that do the transaction and return me a success confirmation. Of course it cost something but they do everything needed to comply legislation and produce digital invoices.
Another alternative is to embed a Paypal (Donate) button.