To cancel the two unwanted items and get your FVF credited by eBay you need to go through the Resolution Centre:
http://pages.ebay.ca/help/buy/resolving-problems.html
As a seller, the Resolution Center will help you when:
However, before you start that process, it is important to communicate the process with the buyer.
Explain that eBay will send him two requests to cancel the unwanted items. He MUST reply to those requests and accept the cancellations.
Too often we have seen sellers sending cancellation requests to be denied by buyers because buyers did not understand the process. If the buyer declines the cancellation requests, the FVF will not be credited by eBay.
Good Luck