Dave, to be honest it is something that you can take to whichever degree you feel is right for you. It sounds like you are both happy to be open and honest but also committed. Why don't you have a one night shot and see how you feel in the morning? I would say sit with her and explore your fantasies in terms of what you both find as turn ons. You can then try to find the right permister(s) to share it with, perhaps creating the right kind of scene to fully engage them and...hopefully enjoy it. Also by doing it together you will be able to decide how it makes you feel before either of you do it outside of the relationship.
Hope that helps
