Re: bringing another person in the bedroom, 3 way.
I have found it shocking how many "men loving" women who have had past experiences and/or fantasies about other women. I hate hate labels like "bi". Who can argue as the female form is so beautiful. Kudos to the creator!
I have done this when young and had negative impact and relationship eventually ended. Was much different then anticipated.
Sounds like your mind is made up. I can see the the attraction but, can see of the risks too regardless of the intentions and strength of your relationship. Agree with previous post regarding perhaps limiting "all activities" between you and the 3rd or totally setting bounds and make sure you all have the opportunity to stop at any point if someone wants.
Will a sequel with another guy be expected?
Did not gather how well you know the other person by my quick read but, would think someone you know adds to the complexity and possible problems that may arrise. Despite best intentions don't totally ignore the possibilty of someone developing feelings and/or being hurt. If you have ever slept with a friend with the full intention and discussion of it not changing the relationship you know that it is impossible to do. keep that in mind. I am not being judgemental but, you both are being unfaithful to eachother physically albeit with the other's permission, limitations and in eachother's presence. With that come potential unanticipated risks. Would be interesting to know how things turn out long term.