Official role vs friendship

Last night I had my first appointment with a couple who would like me to be at the birth of their first baby in November.
I took a list of questions with me and after catching up a bit took my list out of my bag. The next hour just flowed as we talked about their expectations and wishes and I barely looked at my paper.
Because we already know each other there were a few moments where I could feel a slight tension in myself between being in this kind of official role and being a friend.
I guess that in this role there will always be that tension. Whether you know the couple before or not, they are inviting you into a very intimate moment in their lives and that must give a certain bond that rates somewhere on the friendship scale.
Of course on my way home I thought of a million things, well not quite a million then, I could have said differently and remembered the things i forgot to mention. Oh well they are for the next appointment.
Another step....closer to my first birth as a doula.