You can use the WooCommerce Checkout Add-Ons extension to add these fields to the checkout page.

The data will form part of the order once the order is submitted, so you can use that to accurately remember which charity each customer wanted money to go to.

Cheers

Hope the previous reply answered your question. We haven’t heard back from you in a while, so I’m going to mark this as resolved – if you have any further questions, you can start a new thread.