I'd keep both of the appointments! if they are really running over (ie if they are attending a birth) they usually re-book you on the spot.

As for hypnobirthing or calmbirthing (very similar techniques/philosophy) I recommend it EVEN IF you do have a c-section. the beauty of such techniques is that they help in releasing all the gorgeous happy hormones that are released in birth anyway (oxytocin is the love hormone...something we produce when we are in love AND having a baby! Mother Nature is marvelous in giving us that gift!). So this way, you and your DH will be able to hold eachothers hand even in the operating room and be able to draw upon your own bodies to release all that gorgeous love hormones that your baby will also be producing (because if you do, they do!) and then when they are born, you are all loved up and it really helps with the bonding etc.