Our reunion committee came up with a question in the spirit of fairness and I can't answer. How can you set up the Event Planner to up charge the credit card processing fee only to those who use that mode? It doesn't appear I can charge different costs in the registration process for checks vs credit cards to pass the costs on.

There is not an option to do this. You could have two ticket prices, but there is nothing to stop a credit card purchaser from buying the cheaper non-credit card tickets.