Thanks for the replies so far, there is definitely a lot to learn from this forum. I (D) just read this article by David Nobles (Thanks to Tantric for posting it in the articles section). I think we are doing a few things right, but I could also see us slipping into some of the pitfalls David detailed. Some of the pitfalls might be must-haves for us, but knowing how to include them will defiantly help us to not create a box to try and stuff someone else into.
Our thoughts were always that coming-out to our friends was the appropriate method. Reserve coming-on-to for Barney Stinson
For quite some time we have discussed bringing another person into our bed but we both agreed that randoms or swinging is not desirable for either of us.
I just re-read our wording here and can understand why we may have come across more like noobs (Not denying that we are poly-noobs right now) We were simply trying to express that we desire that person or couple to share lives with and not just be short-term-physical.
We consider ourselves very lucky to have these two existing couples as friend in our lives. We have already grown very close with them and have strong emotional ties - which we think are reciprocated. Foremost for us is maintaining the connection we already have, if nothing develops further after we come out to them we will still be just as happy and care for them just as we do now. (Of course there is risk that things could go south in any relationship regardless of friends, lovers, hetero, poly...)