That is exactly what and why we did it now. because these people are so important to us, it was important to try and gauge their feelings on the concept level, instead of breaking the news of a real person addition.
I must say it went very well. The outcome was basically that they loved us either way, and that if this would make us happy, they will do everything they can to accept it for what it is.
They gave some advice, everything we have already been thinking about. Like communication, going slow, etc.
I must say it was a huge relief to bring my parents into the fold. I have always known that my parents were huge fans of us kids, and its pretty apparent that they will support and love us no matter what.
I hope this is the groundwork for a great series of events to come.
Thanks for all your support here on the boards, and great advice.