Moduł do shopper, woocommerce, presta

I am looking for a contractor for an "additional payment" module, or rather a donation i.e. on the order finalization page to be an additional module (top-down UNLIMITED) to donate 1, 5, 10 zloty or an amount of your choice (not necessarily) as an additional payment to a purchase in the online store - a donation for my terminally ill son. I have several stores I know that are willing to add such a module. The whole problem is that this payment cannot be included in the sales of a given ecommerce store only has to be a separate transaction/payment to my Son's account so that the familiar stores that add this module do not have to punch it on receipts/invoices and not pay tax on it. Any payments I can hook under this depending on the suggestion of the future contractor. Alternatively, if it's hard to implement this can display at the end after the already proper payment for purchases in the order confirmation, but it will definitely reduce conversions. Informatively my son's website: JakubSikorski.pl