iMac and MacBook Air shared monitor I have used a thunderbolt connection and pressed Command F2 to allow my track pad and keyboard on my MBA to run both screens. However, I want to use the wireless track pad and keyboard that comes with the iMac instead of the laptop track/keyboard. In other words, I would like the iMac to be the primary computer and use the laptop as a secondary screen (with all control remaining with the iMac). Is this possible?
Simple answer, no it's not possible. The Target Display Mode is a function specific to the iMac and this functionality isn't incorporated into MacBooks.

You could of course pair the wireless keyboard and trackpad to your MacBook and use TDM on the iMac, but if you're trying to leverage the iMac's CPU power you're out of luck I'm afraid. You'd be better off buying a small cheap monitor if you need a secondary display for use with the iMac.