"Strange sensation" indeed. We are not into cuckolding, we are just very liberal, but in the end is the same when it comes to "share" your partner or "open" de bedroom. It's a very intimate thing that you are kind of opening the window to. The thing is: be prepared to a mixture of feelings and sensations: lust and jealousy, desire and anger, the wanting of going forward and the fear of loosing something, etc. But, you know what? that's why it is not vanilla but rather a complex flavour with bitter sweet and strong scent.
Pd. Don't forget to communicate with her. Is the most important thing.
Pd2. Enjoy.