Thanks, Barnacle, for your response. I am still hoping to avoid the PCI route if we can - we are a small, all-volunteer organization.
I am pretty confident that PayPal Advanced does not require PCI-compliance. It uses i-frames, so that the tranactional process occurs on PayPal's pages. For this reason, it would be very attractive option for us.
None of this would be necessary if PayPay didnt make it so obtuse and confusing to use credit cards with PayPal Standard.