Bluetooth keyboard to work with Macbook Pro and an iMac as a Display

Hello!

So I have a 27" iMac and a 13" Macbook Pro. Both are on Yosemite Version 10.10.3. I got the iMac to serve as an extension of the display of the MacBook Pro like I wanted, and the Trackpad to pair up with the MacBook Pro as well. However, I cannot get the bluetooth keyboard to work with the MacBook Pro because it is already paired up with the iMac. Kinda tricky...

Any help will be greatly appreciated. It's the only thing stopping me from being able to work on the bigger screen.